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Teachers’ Guide

Lesson Plans: Physics

Preface The Government of Punjab has a strong desire to improve the quality of teaching and learning in the classroom. Various initiatives have been undertaken for provision of quality education to students in the Province. Provision of quality education at secondary level is an important step towards building an education system meant to contribute meaningfully towards development of our society. To achieve the desired goal, activity oriented training for secondary school teachers based on modern teaching methodologies has been considered imperative and crucial. Directorate of Staff Development (DSD) has been training in-service and pre-service public school teachers and developing educational material since its inception. Considering the quality work produced over the years, the task of development of the Teachers' Guides for secondary school teachers in the subjects of English, Physics, Chemistry, Biology and Mathematics was assigned to the Directorate of Staff Development by the Provincial Government. DSD worked in collaboration with over three hundred professionals i.e. Teachers, Book Writers and Teacher Trainers from both public and private educational institutions in the subject of English, Physics, Chemistry, Biology and Mathematics who worked in groups to develop these comprehensive Teachers' Guides. These Teachers' Guides with textbooks are aimed to achieve Students' Learning Outcomes (SLOs) through the teaching materials and methodologies which suit varying teaching and learning contexts of Punjab. These Teachers' Guides will help secondary school teachers to deliver and further plan their content lessons, seek basic information on given concepts and topics, and assess students' understanding of the taught concepts. The DSD team acknowledges the cooperation extended by various public & private, national and international organizations in the preparation of Teachers' Guides. DSD recognizes the contribution made by all developers and reviewers belonging to following organizations including German International Cooperation Agency (GIZ), Institute of Education and Research (IER) Punjab University, Government Science College, International School of Choueifat, Crescent Model Higher Secondary School, Punjab Textbook Board, Lahore Grammar School, Himayat-e-Islam Degree College, SAHE, PEAS, NEEC, HELP Foundation, Ali lnstitute of Education, Beaconhouse School System, ALBBS, The Educators, Divisional Public School, The City School, AFAQ, Portal, LACAS, Children's Library Complex (CLC) and GICW Lahore, Govt. Higher Secondary Schools and Govt. Colleges for Elementary Teachers in Punjab. ( Nadeem Irshad Kayani) Programme Director Directorate of Staff Development, Punjab


Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 1

T O P I C

1

Introduction to Physics

Physical Quantities and Measurement

n de

po

sit ion

bli ma tio

n tio sa en nd on co ati or

gas

ap ev

su

Grade IX

melting

solid

solidification

Students’ Learning Outcomes

The students will describe:  the crucial role of Physics in Science, Technology and Society.  list with brief description the various branches of physics

Information for Teachers  

Physics is a natural science which deals with the study of properties of matter, energy and

1

liquid

their mutual relationship. Physics tires to explain how things work or why things happen.' The laws of physics can describe how objects fall, how light travels, how a rainbow is made, or how a telescope works. Why does an apple fall? Why does light travel in straight lines? Why do magnets attract? Why does water boil? Practically speaking, physics is a guide to action in the complex world of natural phenomenon. The various branches of physics include mechanics, Thermal Physics, Optics, Waves and oscillations, Sound, electromagnetism,


Teachers’ Guide

Lesson Plans: Physics

atomic and Molecular Physics, Nuclear Physics, Plasma physics and solid state physics. There are some branches of physics under which we study the combine concepts of physics and other branches of science i.e. astrophysics, geophysics and biophysics. Discoveries in physics have led to the inventions of thousands of machines that affect our everyday life. Electricity, television, transport, robots and electronics are few examples. All product of modern technology are applications of the principles of the physics. It is vital that students understand the interrelationship of science, technology and society.

Development Activity 1 

Duration/Number of Period 80 mins/2period

Material/Resources Required Black board , Posters including various branches of physics, Textbook of grade IX, beakers, magnet, sprit lamp, prism etc.

Introduction

Activity 

blackboard or chart paper and explain to them that physics is not a body of facts, but rather a process of asking questions, designing experiments and theories to answer those questions which come in mind about the things and happenings around us. We can say that physics tries to explain how things work or why things happen.

Ask the students, do they know that what is happening around us? Can they explain the phenomena like o light travels in straight lines o how sound is produced? o things fall towards ground o conversion of different states of matters o creation of rainbows and o lightening etc. Write students' responses on the

2

Draw a concept map of physics and its various branches on the blackboard. Sample concept map is given on next page. To further strengthen the concepts of students divide them in groups of 5 students and take them to the library to explore the definition of physics and its main branches as given in the concept map. G u i d e t h e m w h e re n e e d e d i n completing their tasks. After the completion of the task, select one representative from each group to present their work. Sum up the activity by sharing with them that whole universe is constituted of matter and energy, physics is that branch of physical sciences which explains the properties of matter and energy and of their mutual relationship.


Teachers’ Guide

Lesson Plans: Physics PHYSICS is the science that deals with the ideas of

Matter

can be studied in terms of its

properties

Energy

can be studied in terms of its

properties

relationships with matter

relationships with energy in the fields of

Mechanics

Thermal Physics

Light, Waves and Sound

Electricity and Magnetism

Atomic and nuclear physics

Activity 2 Divide the class in different groups. Provides the pictures based on the various branches of physics to the students and asks them to discuss it in groups . They can discuss the things with the teacher if they find something difficult . The students are asked to make preparation for the classroom quiz program on the Topic ”Branches of Physics” Classroom Quiz Program sheet

Sr. No 1.

Area of study

Pictures

It is the study of physics which deals with the motion of bodies.

Branch of Physics with relevant natural phenomena

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3


Teachers’ Guide

2.

3.

4.

5.

6.

Lesson Plans: Physics

It examines the structure, properties, and behavior of the atom.

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It analyses the relationship between electrical and magnetic forces.

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Branch of Physics which Examines the structure , properties and behavior of molecules.

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It is concerned with the structure and properties of the atomic nucleus and it deals with nuclear reactions and their applications like fission and fusion reactions

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Optics is the study of nature and behavior of light

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4


Teachers’ Guide 7.

8.

9.

10

Lesson Plans: Physics

Plasma physics is concerned with the study of highly ionized gases -

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The study of the behavior of electric charges and the fields they create in their surrounding space

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A branch of physics concerned with the study of the physical and chemical properties of material objects and energy sources situated outside the boundaries of the earth's atmosphere This is the branch of physics that studies heat and its relationship with other forms of energy.

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Activity 3 

Ask the students to plan a demonstration in pairs showing simple principles of physics and explain their applications in everyday life. Write the following topics on the board: o Metal expand when heated. o Movement of particles o Light travels in straight lines. o Energy cannot be created nor destroyed, thrhoug it can be changed from one form into another. o Lawsof reflection o Magnetism

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Teachers’ Guide

Lesson Plans: Physics

Assessment

Conclusion/Sum up 

Conclude the lesson by recalling the: o definition of physis that it is the branch of science which deals with the study of properties of matter and energy along with their mutual interaction. o various branches of physics. o various aspects of nature that they not only provide us physical comfort through their new inventions and researches but also provide the vital evidences required to understand nature. o Sduty of physics makes students independent inquireres about the natural world

1.

2.

3.

List any three phenomenon occurring around us and explain their application in the society.

Make a list of things in your home that use electricity from the mains and from electric cells.

Describe application of principles of physics in your daily life. Follow-up

ask the students to prepare a list of some technology based instruments that they commonly see when they visit a school, a house and a factory etc.

Questions for Students No.

Hints for Teachers

Questions

Technology based instruments

Effect on the way of life

When you enter the school, what kind of devices do you find over there that operate using some kind of technology?

Computers, Overhead projectors, printer, telephone, cell phone, fan etc

Communication means improved , Service delivery enhanced , learning opportunity increased , Less reading materials required , Bridging with international community of children access to the knowledge world

When you enter in your house, what kind of devices do you find over there that operate using some kind of technology?

Computers, television, microwave oven, Fans, Air conditioners, Refrigerator, Iron, Thermometer Telephones etc

Communication means improved , Comfortable level of living improved , less time required to complete house hold duties , Bridging with the people around the globe

When you enter in some factory what kind of devices do you find over there that operate using some technology?

lifts, electrical fuses , Cars, Computers, elevators, machinery

More production with less effort , quality of products enhanced , work force well managed , communication means increased , bridging with stake holders at the local , national and international level

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Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 2

T O P I C

An introduction to Significant Figures

1

Physical Quantities and Measurement

5

6

7

8

9

Grade IX

10

11

12

13

14

object

Students’ Learning Outcomes

The students will be able to:  describe the need using significant figures for the recording and stating results in the laboratory.

The result of an experiment cannot contain more number of significant figures than the minimum number of significant figures in any of the observed quantities.

The number or numbers, other than the power of 10, which are given in a measurement, are called significant figures they indicate the precision with which a particular measurement has been made.

Determining the Number of Significant Figures here are a few rules to help you determine how many S.F. are in a given

Information for Teachers 

In any measurement, the accurately known digits and the first doubtful digit are called significant figures.

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Teachers’ Guide

Lesson Plans: Physics

number, and which of the digits is the least significant one: 1. Integers are exact and are considered to have an infinite number of S.F.; i.e. 2 is understood to be 2.0000000…. 2. Numerical constants such as can have as many S.F. as you need e.g. 3.14, 3.14159, 3.14159265…. 3. If the number is neither an integer nor a numerical constant, then the number of S.F. is equal to the number of digits excluding certain zeros that act only as "placeholders." In a number with a decimal point, any leading zeros are placeholders and are not significant, but trailing zeros in this case are significant. In a number without a decimal point, trailing zeros might or might not be significant; you can only tell from the context! In any case, the least significant digit is then the significant digit that is farthest to the right. For our purposes, the accuracy of any quoted value can be assumed to be ± 1 of the least significant digit, unless stated otherwise. Here are some examples to help you practice: Sample Number

# of S.F.

Significant Digit

Hints

6

4

all digits are significant

123.000

6

0

trailing zeros after decimal are significant

3

4

100.32

5

2

5400

?

?

Duration/Number of Periods 80 mins/2 period Material/Resources Required Meter rod, pencil, pictures, Board, beaker, vernier calliper, bean, jar and textbook IX. Introduction

123.654

0.000654

Significant Figures in Scientific Notation. As mentioned above, we cannot always take a number out of context and determine the number of S.F. For this reason (and also because scientists get tired of carrying around lots of zeros!) scientists usually write numbers using scientific notation. When we convert a number to scientific notation, we get rid of any nonsignificant zeros.  Significant figures originally come from measurements. When measuring, you may estimate one decimal place beyond what the measuring device shows. When you do this, then: All digits in your measurement are significant except place-holder zeroes. 

Activity 1   

leading zeros are only placeholders, hence not significant middle zeros are always significant don't know-as scale used is not known

Ask students what they think. Is measurement different from counting? Write their responses on the board. Ask students to count windows of their classroom, note their responses on the board. Do all students answer exactly the same?

Activity 2 

8

Invite 3-4 students, provide them a metal strip and a ruler and ask them how long the metal strip is?


Teachers’ Guide 

Lesson Plans: Physics

Record their reading on the board. Are the answers of all students exactly the same? (yes) Explain to students that a measurement is very different from counting, even though both associate numbers with notions. Demonstrate the difference between counting and measuring. Explain it telling the students that we can count the number of beans in a jar, and know it exactly but we cannot measure the height of the jar exactly. There is no such thing as a exact measurement. All measurements include uncertainties. In scientific research most accurate measurement are required. To record the most correct measurement, a scientist always keeps in view the uncertainties in the measurement. Help the students to realize that we often use approximations while discussing measurements. Every measurement, whether it is made by students or a professional scientist, is subject to uncertainty. A digit in a number is said to be a significant figure when it is known with some reliability. If you take your calculator and multiply 1.378 times 2.3 you will get 3.1694 as a result. If you divide 3.7 by 1.336 you will get 2.769461078. These results are "correct" in a pure mathematical sense that assumes you know the values of the initial numbers exactly. That is, that 3.7 is actually 3.7000000000..., that 1.378 is actually 1.378000000000... and so on. In the real world when we make measurements of anything, the value we get is not known exactly, but rather has some uncertainty associated with it.

How large this uncertainty is depends to a high degree on the type of measuring device used as well as how it is used. For example, suppose that three students were told to determine the length of a piece of metal and were given a tape measure whose smallest markings were at 0.1 centimeter intervals.

11

10

12 cm

They report the following values: Student

Value measured for length

1

11.0 cm

2

11.6283476 cm

3

11.6 cm

Who is right, who has quoted a value of the proper accuracy? (Expected answer:

9

Student 1 has been overly conservative because it is possible to estimate how far between the 0.1 cm marks the edge of the wood lies.

Student 2 is being impractical, because it is impossible to estimate such small distances by eye.

Student 3 has made the best estimate of where the edge lies. No accuracy is lost as in case 1, and no unrealistic accuracy is claimed as in case 2. We've assumed here that one can measure accurately to


Teachers’ Guide

Lesson Plans: Physics 

one-tenth of the smallest markings on the ruler—in this case, that means to the nearest 0.1 cm. This example illustrates the general concept of significant figures (hereafter called S.F.) and the accuracy of the least significant digit . 

So student 3's length measurement of 11.6 cm has 3 S.F., with the least significant digit in the one tenths place. Now Student 3 measures instead the width of the same piece of wood and finds it to be 5.7 cm. This result has the same accuracy as the previous measurement (both are given to the one tenths place), but only has two S.F.

Development

Activity 1  

Ask students to measure the length of their physics book. Tell the students to discuss with their neighbour student about the length of the book and take three readings and find the significant digits in the final reading. As a whole group, share ideas and problems. 

10

Then explain to the students, if a student measures the length of a book as 18 cm. the number of significant figures in his/her measured values are two. In the figure 18, the left digit 1 is the accurately known digit. That is the student claims it neither to be 0 nor 2. However for the rightmost digit 8, the student is not very much confident. This digit may be regarded as a doubtful digit as it may be 7 or 9 instead of 8. Thus a number may consist of two types of digits. a) Accurately known digits and b) doubtful digit In any number all the accurately known digits and the first doubtful digit are called the significant figures. Let another student measures the same book using a ruler and claims its length to be 18.5 cm. In this case the student is sure about the digits 1 and 8. 1 and 8 are accurately known digits. However he/she has doubt about the last digit in his/her measurement as he/she regards 18.4 cm or 18.6 cm to be as accurate as 18.5 cm. Thus the last digit 5 in his/her measurement is a doubtful digit. Therefore all the three figures are significant, the two accurately known digits and the one doubtful digit. The precision of a measured value of a physical quantity is reflected in the number of significant figures (or significant digits) used in expressing the values. An improvement in the quality of measurement by using better instruments increases the significant figures in the measured result and at the same time reduces the uncertainty of the result.


Teachers’ Guide

Lesson Plans: Physics

Activity 2  

Write the following on the chalkboard: A=1.24m B=0.23cm. Ask students which measurement has more significant digits Explain to students that A has three significant digits and B has only two significant digits, however, A is a measurement to the nearest centimeter, but B is a measurement to nearest 1/100 centimeter. It is more precise.

Activity 3 Measuring a Piece of Metal Width with a Ruler Showing Centimeters, divided the class in two groups by saying you are measuring the width of this piece of Metal with a ruler that only showed centimeters (cm).

The ruler shows centimeters so we’re allowed to estimate one more decimal place than cm-in other words to tenths of a cm.

The piece of Meatal looks to be around 6.5 or 6.6 cm cm

6

(not actual size)

7 6.5

6.6

We can estimate this piece of Metal's width as, for example: Studetn from Group 1

We cannot estimate this piece of Metal's width as, for example: Studetn from Group 2

1 place past cm. 1 place past cm. OR 6.6 cm 6.5 cm

2 places past cm. 2 places past cm. OR 6.57 cm 6.58 cm

The last digit is significant but uncertain and is in the tenths place. Note: Technically we could say the width is 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, or 6.9. But 6.4 and 6.5 look the closest to me.

We're trying to go two decimal places beyond cm, to hundredths of a cm. Scientists allow estimates this accurate using this particular ruler.

2 significant figure are allowed here.

3 significant figure are NOT allowed.

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Teachers’ Guide

Lesson Plans: Physics

Conclusion/Sum up 

It is true of science in general and of physics in particular that its essence is measurement. No fact in science is accepted, no law e sta b l i s h e d , u n l e s s i t i s q u a l i f i e d measurement.

The accurately known digits and first doubtful digit in any measurement is called significant.

Number of significant figures depends i. Size of the object ii. Degree of approximation and iii. Measuring instrument: for example In case of metre rod/ruler having signs of cm and mm, the accuracy of measurement is upto one millimeter (1mm). In case of a varnier caliper with least count of 1/10 mm, the accuracy will be 1/10 of a mm. In case of Micrometer screw gauge with last count of 1/100 mm, the accuracy will be 1/100 of a mm. Greater the accuracy of the instrument, the larger the number of significant figures that can be used: the measurements recorded as: (I) 2.4 (ii) 2.40cm & (iii) 2.400cm specify the use of different instrument.  Non-zero digits are always significant.  All final zeros after the decimal point are significant.  Zero between two other significant digits is always significant.  Zeros used solely as place holders are not significant. 

measurement. Answers a. 245 m 3 b. 0.00623 gm 3 5 c. 1.86000 x 10 m 3 5 d. 1.86 x 10 m 6 e. 308 km 3 2- Identify the correct number of significant digits in each number. a. 0.234 three b. 112000 three c. 13.067 five d. 2.450 four 3- Ask students to record their reading from the given diagram and suggest t he correct number of significant figure. (correct reading 32.0) 40 32.0 30

20

Follow-up 

Why does a vernier calipers gives more accurate reading than as a measuring tape?.

Why it is needed to two round of numbers at the end of calculations?

Why does a vernier calipers gives more accurate reading than as a measuring tape?.A sporting goods store is advertising a breakthrough in stop watches. The new model can measure to 1/1000 of a second. Ask students to write a paragraph explaining whether such a watch would be useful. (hint: Students should realize that this watch is a triumph of technology but that it doesn’t make any sense to buy such a watch when the human reaction time is about 1/10 second.

Assessment 1- State the number of significant digits in each

12

Solve all the questions given at the end of the chapter


Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 3

T O P I C

2

Drawing and Interpreting Graphs

Kinematics

Grade IX

d(t)

t

d(t) 100 10

10

20

30

40

Students’ Learning Outcomes

   

Identify various types of graphs Draw and display given data in the form of a graph Recognize linear direct and inverse relationships Interpret a graph by describing the information provided by it

 

Information for Teachers 

Drawing & interpreting graphs is one of the important skills applied not only in

13

50

60

t

mathematics and sciences but also in all other disciplines of social sciences, commerce, business studies etc. Graphs make visual display of data and other numerical information readable easily. A Graph gives visual pictures of results and information regarding relationship between two variable quantities. It can be used to find an average value from a set of readings. It can be used to find value of a quantity which is not actually observed experimentally. It helps to discover error in the experimental observations.


Teachers’ Guide

Lesson Plans: Physics Material/Resources Required

Duration/Number of Periods

Meter stick, String, four Circular objects, Graph paper, Pictures

160 mins/4 period Introduction Activity 1

Arrange to show various types of graphs mentioned below taken from Newspapers / Magazines to initiate discussion on graphs. 1. Bar Graph 2. Line Graph 3. Circle (or Pie) Graph 1. BAR GRAPH i) A bar graph is used to show relationship between groups that are not continuous. ii) The two items being compared do not need to affect each other. iii) Numerical values are shown in bars of varying lengths. iv) Easy to see the comparison of two items v) Multiple comparisons are possible To make a graph:1. Use a suitable scale 2. Label axis and plot data 3. Choose a title representing the data ď‚—

The Effect of Fertilizers on Bean Plant Growth 28.0 25.2 22.4 19.6 Average 16.8 Height 14.0 in cm 11.2 8.4 5.6 2.8 0.0 Figure 1

A

B

C

D

E

2. LINE GRAPH I) A line graph is made from pair of numbers. Each expresses a relationship between two variables. ii) It shows a continuous variation of one quantity affected by another. iii) Line graph shows the effect of independent variable on a dependent variable. iv) It reflects comparison easily. v) Reveals trends of pattern and relationships between data. vi) Widely used in statistics and science.

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Teachers’ Guide

Lesson Plans: Physics

Exercise and Pulse Rate 160 144 128 Pulse 112 Rate 96 in Beats 80 64 per 48 Minute 32 16 0

Time (in Minutes) Sohail: 36 year old office worker Ahsan: 26 year old former college athlete

Figure 2

3. CIRCLE (OR PIE) GRAPH i) A circle graph is used to show how part of something relates to the whole. ii) This kind of graph is needed to show percentages effectively. iii) To draw a pie chart: Find the percentage of each type o  Find the size of wedges that make up the pie chart by multiplying each %age by 360 . (since a circle contains 360o.)  Use compass to draw a circle.  Use protractor to draw required angles.  Finally, label each part of the chart and choose one appropriate title. iv) This type of graph is a circle divided into segments. v) Each segment represents a particular category. vi) Lay out largest portions first in clockwise position. vii) Label larger portion in the circle; smaller outside with connecting lines. An Ice Cream Survey Flavour Vanilla Chocolate Strawberry Respberry Peach Neopoliton Other Figure 3

15

Liking of Persons 21.0% 33.0% 12.0% 4.0% 7.0% 17.0% 6.0%


Teachers’ Guide

Lesson Plans: Physics

Activity 2

axis not the actual number. (f) Points to be plotted with: Cross (x or +) or with dot and circle ( ) [Fig 5].

Now tell the students how graph is plotting PLOTTING A GRAPH Every Graph shall have: (a) A title: On top of the sheet such as “Load against Extension” (b) Axes to be labeled: Normally cause (independent variable) on X-Axis and the effect (dependent variable) on y-axis but it is not essential. Write clearly the name of each variable giving its unit [Fig.5].

Load L (N)

Load against Extension

Scale 2 cm = 0.5N Scale 2 cm = 20mm

Title Figure 5

Extension e (mm)

(g) Drawing curve: The plotted points must be joined with single straight line. Do not attempt to join all points on the graph .If the points do not seem to lie on a straight line, draw a free hand smooth line (continuous curve) passing evenly through most of the points.

Label/Unit ordinate or y-axis Scale for y-axis Scale for x-axis

Label/Unit abscissa or x-axis Figure 4

( c) Suitable scale: Do not condense the graph into a small area but make it fill the whole sheet. This requires a suitable scale for each axis [Fig.5]. Draw a graph as large as the available space allows. Scale should have 0, 1, 2, 3 ---- or 0, 2, 4, 8 ---- or 0, 5, 10, 15 sequence. Odd sequence such as 0, 3, 6, 9 — or 0, 7, 14 should not be used. (d) Selected scale to be mentioned: Same scale on both axes not essential. Even zero of the scale not necessarily to lie on the origin [Fig.5]. (e) Graduation: Make scale on each

(h) Best straight line: Try to draw a straight line which passes through as many of plotted points as possible or which leaves on equal distribution of points on either side (Figure 6). a. A transparent ruler is very useful for drawing this line. b. Statistical Method: simply mark with different notation, the mid points for each pair of plotted points. The mid points usually lie nearly on a straight line. The process usually can be repeated until a straight line is obtained.

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Teachers’ Guide

Lesson Plans: Physics

y

which is linear equation of a straight line through the origin. It means y is directly proportional to x, where m is content. If straight line does not pass through the origin than y = mx + c where c is the intercept on y axis. Examples: The relations of this type are of Ohm's law & Hooke's law. Slope and Intercept Gradient (slope) of a straight line is the tangent of the angle θ which the line make with the horizontal. In case of Pd 'V' and current 'I' the slope of the line gives the resistance. The slope m in the above equation is the ratio of vertical change to the horizontal change. For that purpose select two points A and B, as far apart as possible on the graph line. The vertical change ∆y is the difference between the vertical values of A and B. The horizontal change ∆x is the difference between horizontal values of A&B. The Slope m = ∆y / ∆x

0

x

Figure 6

(I) Conclusion: State and display the conclusion drawn from the graph. In the given example, a straight line graph through the origin confirm that ex tension in length is proportional to applied load (Fig.5) STRAIGHT LINE GRAPH It is often useful to plot experimental data in such a way that straight line graph results. From the straight line graph OA, by completing right angled triangle line OAM, A (x,y)

B

y2

y V

∆y A

y1

θ

∆x M

O

x

Figure 7

θ

x1

x2

O

y AM = x OM Let Tan θ = m (Slope or Gradient of the line) y Then m = x Or y = mx Tanθ =

I

Figure 8

Evidence of how a reading is taken from the graph must be shown. e.g. (a) The triangle for calculation of gradient (b) reference line

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Teachers’ Guide

Lesson Plans: Physics

(broken lines) to fine a point on the horizontal axis corresponding to a point on the vertical axis or vice-versa. Intercept: It is the point at which graph line crosses the y-axis known as y intercept. Inverse Relationship: Another common situation occurs when one quantity varies inversely with other quantity y = k/x, the graph of such relationship is a hyperbola (Fig 9).

Development Activity 1 Ask students to make a list of direct relationship and inverse relationship. Discuss their responses in the class.

Activity 2 

Total Pressure P as a Function of Volume V for Gas

P

T = Constant

 

V

Figure 9

Quadratic Relationships: Sometimes a quantity varies as the square of some other such as y = ax2. The equation of this type is known as a quadratic equation and its graph is a parabola (Fig.10).

Conclusion/Sum up 

 Braking Distance (m)

Braking Distance Versus Original Speed 80

 60 40

20 0

0

5

10

15

20

25

Use a meter stick to measure the diameter of four circular objects and a string to measure their circumference. Record your data in a table. Make graph, the circumference versus the diameter. What type of relation is shown by the graph between circumference and diameter? Could a different straight line describe a different circle?

30

Original Speed (m/s)

 Figure 10

18

A graph in which data points lie in a straight line is a graph of linear relationship. A linear relationship can be expressed by the equations y = mx + c. The slope 'm' of the straight line graph is a vertical change divided by the horizontal change. The graph of an inverse relationship between x & y is a hyperbola represented by the curve y = a/x. The graph of quadratic relationship is a parabolic curve represented by y = ax2 + bx+c


Teachers’ Guide

Lesson Plans: Physics Follow-up

Assessment 1. A student performing an experiment with the simple pendulum determined the time period 'T' for various lengths 'l' of the pendulum. The data is tabulated below: l(cm) 2

2

T (s )

60

65

70

75

80

85

0.6

1.0

1.27

1.81

1.91

1.96

Plot a graph with 'l' along the x-axis and T2 along the y-axis using a suitable scale. ii. Which variable is dependent variable? iii. From the graph, determine the value of 'l' for second's pendulum. 2. In an experiment the value of g was determined by free fall method. It was observed that the distance of fall (S) of the bob from its initial position and the corresponding time period (T) of the rod have a certain relation. A few values of S and the corresponding time period square T2 are tabulated below: i.

Distance, S (cm) Time Period 2 2 squared T (S )

20

30

40

50

60

0.65

0.95

1.30

1.55

1.90

1. A student performing an experiment with the helical spring obtained the following data for loads 'L' and the corresponding extensions∆ x.

i.

L (g)

50

100

150

175

200

x (cm)

3.4

6.8

12.0

13.4

16.0

Draw a graph between 'L' taken along x-axis and '∆ x' along the y-axis, using a suitable scale. ii. Which is the dependent variable? iii. Determine the spring constant and give its units. 2. Students will collect different types of graphical sketches printed in some Newspapers / magazines and share with peers the information displayed by them. The conclusions should be posted on the wall or softboard in the form of posters.

i.

Plot a paragraph between a taken along abscissa and T2 taken along ordinate. ii. Find the slope of the graph. iii. In case of free fall, what does this slope stand for?

19


Teachers’ Guide

Lesson Plans: Physics

UNIT

2

Lesson Plan 4 T O P I C

Graphical analysis of Motion

Kinematics

Grade IX

Constant Velocity

Time Period

Displacement

Students’ Learning Outcomes

  

Information for Teachers

Plot and interpret distance- time graph and speed- time graph. Determine and interpret the slope of distance – time and speed- time graph. Determine from the shape of the graph the state of a body when it is: 1. At rest 2. Moving with constant speed 3. Moving with variable speed

20

We can represent the changing position of a moving object by drawing a distance-time graph. The slope of the graph tells us about its speed. The steeper the slope, the greater the speed is. We must assume that the object is moving in a straight line.


Teachers’ Guide

Lesson Plans: Physics

The straight line shows that the object is moving steadily; its velocity is constant. Distance - time graph (I) As a convention, we usually start from the origin, i.e. S = 0 when t = 0. s

(v) This displacement - time graph is curved. The slope is changing. This means that the object's velocity is changing.

s

t

t

gre

ate r

sp

ee

d

(ii) The slope tells us which object is moving faster. The steeper the slope, the greater the velocity. s

ed

e low

pe rs

t

(iii) The slope of this graph is 0. Displacement s is not changing. Velocity v = 0. The object is stationary.

Speed-Time graph The slope of the speed-time graph tells us whether the speed has been changing at a high rate, at a low rate, or not changing at all.  Acceleration is deduced from the slope of speed-time graph.  Acceleration = gradient of speed-time graph. (I) A straight line shows constant acceleration 

v

s

t t (iv) The slope of this graph suddenly becomes negative. The object is moving back the way it came. Its velocity v is negative.

(ii) The greater the slope, the greater the acceleration

s

v

r ate n greleratio e acc

ration

lower accele

t

t

21


Teachers’ Guide

Lesson Plans: Physics

(iii) A negative slope shows declaration (a is negative) v

t

(iv) The slope is changing; the acceleration is changing v

t

Duration/Number of Period

used as guidelines:  Ask your classmate to throw a ball vertically upwards and observe the motion of the object.  Is its initial speed zero?  At the highest point of its journey, what is its speed? What do you think its acceleration at that point?  What can be the source of error in this activity?  Try sketching the speed-time graph to describe the motion of the ball from the time it is thrown upwards to the moment your classmate catches it again. Development

80 mins/2period Material/Resources Required

Activity 1 

Graph paper, pencil, rubber, sharpener, ball, chart papers, showing pictures

Distance from start

Introduction Activity 1 Ask students about various ways to present data. From the feedback of students, highlight the importance of graphs as an alternate method to represent the motion of the body graphically and to solve problems of motion / or visualizing the relationship between the physical quantities.

We can calculate the speed of an object at different times during its journey using a distance-time graph. The distance-time graph below shows the journey of a cyclist 300m

C

D

90s

150s

200m 100m

B E

A 50s

180s

Possible Answers to Teacher  Have the students describe motion from A to B, B to C, C to D and form D to E. they should also calculate speed during each interval.  Between B and C the cyclist is travelling more quickly away from his starting point. His speed during this part of his journey is distance travelled / time

Activity 2 Students will be asked to conduct experiment and following points can be

22


Teachers’ Guide

 

Lesson Plans: Physics Activity 3

taken = 200m / 40s = 5m/s. Between C and D the Cyclist has stopped. Between D and E the cyclist is travelling very quickly back towards his starting point. His speed during this part of his journey is distance = 300 - 0 = 300 = 10ms

 

Draw t he following distance-time graph and table on the board. Ask the students to fill the descriptions in the table.

distance (m)

E

-1

30

Activity 2 

10m/s

A 0

F

A

B

50s

10

From t=

To t=

(A)

0s

5s

(B)

5s

10s

(C)

10s

15s

(D)

15s

20s

15

20

Description

at t = 20s

Possible answer for teachers only

D 90s

5

Graph

(E) C

time/s

D

0

Spent

E

C B 10

Ask the students to describe the motion for A to B, B to C, C to D, D to E and for E to F. Tell them also calculate the acceleration during each interval. Help them if needed.

5m/s

D

20

Spent

180 - 150

150s

180s

Possible Answers for Teachers  Between A and B the runner travels at a constant speed of 5 m/s for 10s. There is no change in his velocity so his acceleration is zero.  Between B and C he takes 5s to slow down and stop. His declaration during this part of his journey is change in velocity / time taken = 5 / 5 1 m/s2.  Between C and D he remains stationary for 10s. His acceleration is again zero.  Between D and E he increases his speed to 10 m/s in 5s. His acceleration during this part of his journey is change in velocity / time taken = 10 / 5, 2 m/s2.  Between E and F he travels at constant velocity of 10 m/s for 5 s and his acceleration is zero.

Graph

From t=

To t=

Description

(A)

0s

5s

The object start from rest and moves with constant speed of 2 m/s

(B)

5s

10s

The object is at rest (0 m/s).

(C)

10s

15s

(D)

15s

20s

The object moves with increasing speed The object moves with decreasing speed The speed of the object is more than 20 ms-1

(E)

at t = 20s

Activity 4 Interpreting a Speed – Time Graph Below is a speed-time graph that describes the motion of an object over 70s. Which part(s) of the graph show(s) that the object is a) At rest? b) Moving with uniform speed? c) Moving with uniform acceleration? d) Speed/m s-1

d) Moving with non-uniform acceleration?

23


Teachers’ Guide

Lesson Plans: Physics

Speed/ms-1

(E)

15 (D) 10

(F) (C) (B)

5 (A)

0

10

20

30

40

50

60

70

time/s

Possible answers Graph

From t=

To t=

(A)

0s

10s

The object accelerates from rest (0 m/s) to 5 m/s with a constant 2 acceleration 0.5 m/s

(B)

10s

20s

It is moving at a constant speed of 5 m/s.

(C)

20s

30s

(D)

30s

40s

It increases its speed from 5 m/s to 12 m/s with an increasing acceleration It increases its speed from 12 m/s to 15 m/s with a decreasing acceleration.

(E)

40s

50s

It is travelling at a constant speed of 15 m/s.

(F)

50s

60s

The object decelerates from 15 m/s to 3 m/s with a constant 2 deceleration 0.5 m/s

(G)

60s

70s

It decreases its speed from 3 m/s to 2 m/s with a decreasing declaration.

Description

Comparison of distance-Time and Speed-Time graphs for a body: 1. At rest 2. Moving with constant speed 3. Moving with variable speed Motion of object

Distance-time graph gradient=0

Distance

Speed-time graph Speed

Gradient = 0 Speed = 0

At rest

Time

24

Time


Teachers’ Guide

Lesson Plans: Physics

Gradient constant Distance

Gradient = 0

Speed

Moving with uniform speed

Time Gradient varying

Distance

Time gradient constant

Speed

Moving with uniform acceleration

Time

Time

Assessment

Follow-up

1. Analyzing motion of a body at A, B, C and D

with the help of Distance-Time graph. distance/m D

Plotting the Speed-Time graph and answering short question based on that graph The table below shows how the speed of a car varies with time. Time 0 /s Speed 0 /m s-1

C B A

1

2

3

4

5

6

7

8

9

10

5

10

15

20

25

30

30

30

30

30

a) One the axes provided below, plot a graph of

time/s

speed against time.

2. Show the s-t graph of a stone projected

vertically upwards at 40 m/s. S(m) 80 60 40

b) (i). Calculate the total distance travelled by

20 1

2

3

4

5

6

7

8

t (s)

a) How long does it take the stone to reach its

highest point? (Ans: 4 s) b) What is the greatest height reached? (Ans: 80m) c) What is the time of flight? (Ans: 8 s)

25

the car at the end of 30 s. (ii) Hence calculate the average speed of the car.


Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 5

T O P I C

4

Moment of a Force

Turning Effect of forces

Grade IX

F M

d

Force Moment

Distance Students’ Learning Outcomes

Information for Teachers

Students will be able to: 

define moment of force or torque as moment = Force x perpendicular distance from pivot to the line of action of force.

explain the turning effect of force by relating it to everyday life.

state the principle of moments.

define the center of mass and center of gravity of a body.

26

Moment of a force or torque is the turning effect of a force. Torque depends upon the magnitude of force and the perpendicular distance of the force from the pivot. It is easier to tighten up a nut with a spanner, to open the cap of a bottle with opener, to open the door from the knob rather than near the hinge. All these examples give rise to the


Teachers’ Guide

 

Lesson Plans: Physics

turning effect of forces. There are two types of moment of force. a. Anticlockwise moments b. Clockwise moments Principle of moments states that when a body is in equilibrium the sum of clockwise moments and anticlockwise moments about any point is zero. Center of gravity is that point where the whole weight of a body appears to be acting. The forces which have same direction are called like parallel forces and the forces which have opposite directions with each other are known as unlike parallel force. When two equal and opposite parallel forces act on a body on two different points they produce torque in the body and the pair of such forces is called couple. Bicycle pedal, car steering, water tap knob and cross spanner are some examples from daily life in which couple of forces make them to rotate. There is no difference between center of mass and center of gravity as long as 'g' remains same over the system.

Material/Resources Required Metre rule, wedge, a chart having drawings of different objects etc.

Moment of Force or Torque

Anticlockwise

Clockwise =

Principle of Moments

Calculated by =Fxd

Duration/Number of Periods 80 mins/2 period

27

Introduction Activity 1 Get three students and ask them to balance a metre rule on their finger tips turn by turn. Each student will make the metre rule balanced on his finger after a little effort. Now introduce the students the concept of C.G by telling them that the point where the body gets balanced is the C.G of the bodies.

Activity 2 Choose two students with half metre rules. Ask them to hold the metre rules from the ends. Ask one student to release the both ends of the metre rule simultaneously. The metre rule falls freely. Now allow the other student to release only one end of the metre rule, the rule swings down around the other end. After this activity introduce the students about the turning effect of a force and the axis of rotation.


Teachers’ Guide

Lesson Plans: Physics are equal. Now state the principle of moments for a body to be in equilibrium as: Anticlockwise moments = clockwise moments After these activities ask the following questions to the students i. What is moment of force? ii. What is the formula to calculate moment of force? iii. What are the possible types of moments Expected answers: i. Turning effect of a force ii.  = F X d Clockwise and anticlockwise

Activity 3 Get a student to open the class-room door as usual. Ask him to open the door by pushing near the hinge. Close the door and again let him open it by pushing the knob. Now ask him, where he realizes difficulty in opening the door? Get this activity by few more students. Note their response on the board. Now introduce the concept of moment arm and how it affects the torques.

Development Activity 1

Activity 4

Draw a diagram of three spanners of different lengths opening a nut. m

10

6c

cm

m

10N

d=

d=

8c

d=

Draw the following diagram of sea-saw on the board in which two students of equal weight are sitting at the same distance from the pivot.

12N

8N

Ask the students to calculate the moment of force from the given data.

Spanners Force Moment arm Call one of the student to show the direction of moment of force by drawing an arrow head for both the students enjoying sea saw. From this activity introduce the concept of anticlockwise and clockwise moments. Tell the students that when both the clockwise and anticlockwise moments cannot make the sea-saw rotate then they

1 2 3 

28

10 N 12 N 8N

8 cm 6 cm 10 cm

Which spanner can move the nut more easily? (Expected answer: spanner 1 and 3) Why spanner with 10 N and 8 N forces


Teachers’ Guide



Lesson Plans: Physics

produce the same moment? (Expected answer: as both the spanners have same moment of force) Which spanner would you like to use? Expected answer: Spanner 3

effort P

Activity 2 Show the chart to the students on which the following diagrams with pivot, applied force and the perpendicular distances are drawn. Ask various students to indicate the types of moments; clockwise or anticlockwise in each diagram and record their answers on the board.

Fig: 4 Fig: 5

effort P

spoon

Fig: 2

effort P

load W

effort

Fig: 1

load W

lid

Tin can

Fig: 6 Expected Answers: 1. Clockwise 2. Clockwise 3. Clockwise 4. Anti-clockwise 5. Anti-clockwise 6. Anti-clockwise

Effort Fig: 3

29


Teachers’ Guide

Lesson Plans: Physics

Activity 3 To investigate the principle of moments Q.2

Help the students to set the metre rule balanced on a wedge.  Take two weights of 50g mass (W1) and 100g mass (W2) and tie them with thread loops.  Hang these weights with the help of loops on both sides of the metre rule and balance the system by adjusting their distance from the pivot.  Now change the positions of the weight so that the system is balanced again. When the metre rule is balanced, ask the students to calculate the clockwise and anti clockwise moments. Are these moments equal. 

Q.3

Follow-up

Conclusion/Sum up

Go with your parents in a nearby children park on the coming Sunday and enjoy sea-saw with your brother or sister and observe the effect of moment arm in swinging sea-saw and search different distances from the pivot to get the same swing each time.

Solve all the problems about torque and principle of moments given at the end of the chapter/unit.

 Moment of force is the turning effect of force

and is the product of force and moment arm.  Anti clockwise moments = clockwise moments.  There is no difference between center of mass and center of gravity as long as 'g' remains same over the system.

Assessment Q.1

enjoy see-saw by producing equal and opposite moments. This can be achieved simply by adjusting their arm lengths.) Is it possible for a body to be in equilibrium under the action of a single force? (expected answer: A body can never be in equilibrium under the action of a single force. A counter force in necessary required for the body to keep in equilibrium. what is the difference between centre of gravity and centre of mass? (expected answer: There is no difference between center of mass and center of gravity as long as 'g' remains same over the system.

how is it possible for a young boy to enjoy see-saw with his father although he is much lighter than his father. (expected answer: The young boy and his father may

30


Teachers’ Guide

Lesson Plans: Physics

UNIT T O P I C

4

Equilibrium

Turning Effect of forces

Grade IX

Students’ Learning Outcomes

Students will be able to:  define equilibrium and classify its types by quoting examples from everyday life.  state two conditions of equilibrium of a body.

Information for Teachers 

Lesson Plan 6

When a number of forces act on a body and the resultant of these forces is zero then a

31

body at rest will remain at rest and a body in motion will remain in motion with uniform velocity. In both cases we say that the body is in equilibrium. In the first case the body is said to be in static equilibrium while in the second case it is said to be in dynamic equilibrium. A book laying on a table, an electric bulb hanging from the ceilings of a room are the examples of the bodies which are in static equilibrium. Falling paratroopers, a moving vehicle with uniform velocity, rotation of earth are the


Teachers’ Guide

Lesson Plans: Physics

examples the bodies which are in a dynamic equilibrium. There are two conditions for a body to be in complete equilibrium. First condition states that the body will be in equilibrium if the vector sum of all the external forces acting on a body is zero. F1 + F2 + F3 + …………………….. + Fn= 0 F=0 Second condition of equilibrium states that the body will be in equilibrium if the algebraic sum of all the torques acting on the body is zero

Both the teams make effort, but no one team can pull the other and thus the rope does not move. Knock out a student from any one of the team and again start this contest. After a little effort a team with three students will pull the rope.

Ask the following questions to the students. 1. Why both the teams cannot move

the rope in the first contest? (Expected answer: Both the teams pull the rope with equal force)

1 + 2 + 3+…………………. n = 0 

2. Why did the team with three

 = 0 A body will be in complete equilibrium if it satisfies both the conditions.

students pull the rope in the second co nte st ? ( E x p e c te d a n swe r : Because the team of three students pulls the rope with greater force as compared to the team comprising of two students).

Duration/Number of Periods 80 mins/2 period 

After this activity introduce the students that when forces acting on a body are equal and having same line of action they cancel each other and the body upon which these forces act cannot move. We say that the body is in equilibrium. Tell the students that the hanging bulb in the class room and a book lying on the table are the examples of the bodies to be in equilibrium. As these bodies are at rest, therefore, they are said to be in static equilibrium.

Students are already familiar with uniform velocity and Newton's first law of motion. Tell the students that the bodies in uniform motion are also in equilibrium, which is called dynamic equilibrium.

Material/Resources Required board, chalk/marker, rope, card boards, textbook Introduction Activity 1 

Arrange a tug-of-war contest in which two teams having three students each pull the rope towards each other. Ask all the other students to watch this contest keenly.

32


Teachers’ Guide

Lesson Plans: Physics

Activity 2 Development Activity 1 (Board activity) Card 1

Draw a table on the board and fill it with the help of students and ask the students to copy it on their note books.

Card 2

Cut two rectangular card boards and make two holes on each of them as shown in figure. Tie the cards from these holes with two pieces of thread.  Take two students from the class and give them card-I. Ask them to pull the free ends of the thread. Both students pull the thread and the whole class observe that the card neither moves linearly nor it rotates. Now give them the second card and ask them to pull the free ends of the thread. In spite of applying equal and opposite forces, the card does not remain at rest. It moves clockwise.  Ask the following questions from the class: Q.1: What kinds of forces act on the first card? (Expected answer: Unlike equal parallel force) Q.2: What kinds of forces act on the second card? (Expected answer: Unlike equal parallel force). Q.3: Why the card 1 remains at rest while the card 2 rotates? (Expected answer) a. In card 1, forces act along the same line and no torque is produced. b. In card 2 forces do not act along the same line and thus a torque is produced.  At the end of this activity tell the students that although both the cards were satisfying first condition of equilibrium even then the card 2 was not in equilibrium. Therefore, second condition is also necessary for a body to be in complete equilibrium. Write the second condition of equilibrium on the board. 

No.

Objects

Type of equilibrium

1. A man sitting in a chair 2. Falling of paratrooper A moving car with 3. uniform velocity 4. Rotation of Earth 5. A hanging lamp

Expected answer

Type of equilibrium Static 1. A man sitting in a chair equilibrium Dynamic 2. Falling of paratrooper equilibrium Dynamic A moving car with 3. equilibrium uniform velocity Dynamic 4. Rotation of Earth equilibrium Static 5. A hanging lamp equilibrium

No.

Objects

Activity 2  

33

Draw the following diagrams and the table on the board. Ask the students to copy and fill the table about satisfying the 1st and 2nd condition of equilibrium.


Teachers’ Guide

Lesson Plans: Physics F

F1

F1

Fig 1

Fig 2

F

Fig 3

F

Fig 4

F2

F2

About 2nd condition of Equilibrium

About complete Equilibrium

Fig 1

About 1st condition of Equilibrium Satisfied

About 2nd condition of Equilibrium Satisfied

About complete Equilibrium Body is in equilibrium

Fig 2

Satisfied

Not Satisfied

Body is not in equilibrium

Fig 3

Satisfied

Satisfied

Body is in equilibrium

Fig 4

Satisfied

Not Satisfied

Body is not in equilibrium

Objects

About 1st condition of Equilibrium

F

Fig 1 Fig 2 Fig 3 Fig 4 Expected response of the students will be as. Objects

Conclusion/Sum up A body is in equilibrium if it satisfies both the conditions of equilibrium: a. A body will be in equilibrium if the algebraic sum of all the forces acting on it is zero b. A body will be in equilibrium if the algebraic sum of all the torques is zero. 

balance each other and he starts to fall with constant velocity and thus gains a dynamic equilibrium. Q.2: How can you find the weight of a meter rule without using physical or spring balance? (Expected answer) o Balance the meter rule at the point other than C.G with the help of a given weight. Now by applying the principle of moments the weight of the meter rule can easily be found.

Assessment

Follow-up

Ask the following questions to assess the students learning. Q.1: How does a paratrooper gain its dynamic equilibrium? (Expected answer) o When a freely falling paratrooper opens parachute, his weight and air friction

  

34

Identify two examples in which single force is used to turn the object Identify two examples of the objects in which two forces are used to turn them. Solve the problems given at the end of the chapter.


Teachers’ Guide

Lesson Plans: Physics

UNIT T O P I C

4

Stability

Turning Effect of Forces

Grade IX

Students’ Learning Outcomes

b. Unstable equilibrium c. Neutral equilibrium

Students will be able to: 

Describe to states of equilibrium and classify them with common examples.

Explain effect of the position of center of mass on the stability of simple objects.

Information for Teachers 

Lesson Plan 7

There are three states of equilibrium a. Stable equilibrium

35

The equilibrium of the bodies is affected by the position of center of mass or center of gravity. A body will be in stable equilibrium if on slightly disturbing, its center of gravity is raised up as compared to the initial position. If on slightly disturbing, the C.G of the body is lowered as compared to its initial position the body will be in unstable equilibrium. If on slightly disturbing, the C.G of the body


Teachers’ Guide

Lesson Plans: Physics

neither lowers nor raises but keeps the same position then the body will be in neutral equilibrium. Stability plays an important role in our daily life. It is an important factor which is kept in view in architecture and manufacturing the bodies of the vehicles. Unstable objects may lead to severe accidents, causing great loss of property and lives. Duration/Number of Periods

80 mins/2 period Material/Resources Required Wooden block, ball, pencil, a stiff cardboard, a pair of scissors, sticky tape, common pins. Introduction Activity 

Take a pencil, a wooden block or a board duster and a ball.

Mark their center of gravity carefully with red marker.

New C.G. C.G.

block. It will come to its initial position. Write the following questions on the board. Q.1: What happen with the C.G when the block was lifted? (Expected response: The C.G was raised. Q.2: What happened with the block when it was released? (Expected response: It came to its original position. Now generate the concept that when a body is slightly disturbed and its C.G raises as compared to its initial position, the body is in stable equilibrium. Repeat this activity with pencil standing erect as well as a rolling ball and develop the concept for unstable and neutral equilibrium by asking the same questions as given above.

C.G.

C.G.

C.G.

New C.G.

C.G.

New C.G. C.G.

Place the block with rectangular base and ask a student to keep a scale vertical along its one of the edge and note the position of its C.G. Ask the other student to lift the block up from one side and again note the position of its C.G. Now release the

Development Activity 1 Draw the following diagrams and the table on the board.

36


Teachers’ Guide

Lesson Plans: Physics

1

2

3

4

5

6

No.

the tips. Does it stay at its beak; if not try to adjust the position of the coins again.  When the position of the coins is correctly adjusted the bird will become stable on its beak. Now if it is slightly disturbed then after swinging, it will again become stable. On completing this activity ask the following questions to the students. Q.1: What happened to the C.G when the coins added to the wings of the bird? (Expected answer: Lower the position of C.G) Q.2: How do you think that you could make the bird even more stable? (Expected answer: By increasing the equal number of coins on both sides.

State of State of No. Equilibrium Equilibrium

1.

4.

2.

5.

3.

6.

The expected answers:

No.

State of State of No. Equilibrium Equilibrium

1.

Stable

4.

Unstable

2.

Unstable

5.

Stable

3.

unstable

6.

Neutral

Activity 2 

 

Ask the students to investigate that lowering of C.G makes the bodies balanced. Help the students in performing this activity. Cut the stiff card board in the shape of a bird as shown in figure. Ask the students to find C.G of the card board with the help of plumb line. Guide the students that C.G. of this bird shaped cardboard will be near to the neck. Fix a pin at its beak and tape the coin, underneath the wings of the bird near

Conclusion/Sum up  There are three states of equilibrium which

depend upon the position of C.G of the bodies.  Stability plays important role in manufacturing vehicle bodies, toys and in architecture etc.

37


Teachers’ Guide

Lesson Plans: Physics Follow-up

Assessment Q.1:

What are the factors that affect the stability of an object? Expected answer: I. Position of centre of gravity ii. Area of the base Q.2 Why is it dangerous to load the roof of an empty mini bus too heavy? (Expected answer: On a little tilt the line of action of the loaded bus will come out of the base and the bus may topple. Q.3: Why hanging objects are stable? (Expected answer: Because the centre of gravity of the hanging bodies is below the pivot or point of suspension.) Q.4: Which of these glasses is the most stable? Explain your answer.

(Expected answer: c C has the widest base and is heavier at the bottom.)

38

Why is it possible to balance a metre ruler at its midpoint but it is not possible to balance a billiard stick at its mid point? Explain. Visit a toy shop and identity the balancing tricks in a. Self righting toys b. Racing toy cars c. Rocking chairs Solve all the problems gives at the end of the chapter.


Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 8

T O P I C

6

Power

Work And Energy

Grade IX

washing machine motor 250 W

human engine 400 W

Land rover engine 65 000 W (65 KW)

small car engine 35 000 W (35KW)

Information for Teachers

Students’ Learning Outcomes

The students will:  define power and calculate power from the formula Power = workdone timetaken  

Define the unit of power “watt” in SI and its conversion with horse power Compare personal power developed for running upstairs versus walking upstairs using a stopwatch.

Power is the rate of doing work.

Power depends upon the amount of work done and time taken.

Power is calculated using the equation:

workdone Energy Changed or Power = timetaken timetaken  The relationship between force and power is Power = Force x Velocity P = F.V N.m sec Power =

39


Teachers’ Guide 

Lesson Plans: Physics

Power may also be defined as the product of force and velocity.

The unit of power is watt (w).

The power consumed or used is said to be one watt if one Joule of work is done in one second.

The multiples of watt are

Kw = 103watts Mw = 106 watts

One horse power is the power delivered by a horse as an engine (746 J/Sec) o One horse power is about ¾ kw o One horse power = 746 w The slope of energy-time graph gives power Joule watt = Second

Energy

Introduction Activity Recall the previous knowledge by asking following questions to students Q: what is the meaning of “work” in science? (Work is done when a force makes an object move). Q: what is energy? (Energy is the ability to do work).  After getting responses from students explain to them that we have never seen energy, but we have seen what it does. People who have a lot of energy may move rapidly or do a lot of work.  Introduce the today's topic, power and share with them that power is that rate at which work is done, or energy is transferred. Its SI unit is watts (w).  Invite one student to derive the unit of power from its definition on the blackboard. Guide him/her where needed. 

Development

time/s 

Faster your work greater is your power Activity 1 

Duration/Number of Periods

80 mins/2 period

Material/Resources Required Board, chalk/marker, posters of relevant pictures, stop watch

40

Place four to six books at different places in the classroom Ask two students to collect all the books as quickly as possible Assign another student to note the time in which both the students collect these books Ask the rest of the class to assess who has collected first and who is more powerful than the others


Teachers’ Guide 

Lesson Plans: Physics

Ask the students to conclude the activity by explaining that which student took less time to complete the task is more powerful.

Activity 2 

Ask the students to measure your power output

Guide them in following steps 1. Measure your mass 2. Work out your weight 3. Measure height of stairs 4. Calculate work done when you climb stairs 5. Measure time taken to climb stairs by running. If possible, use a stop watch for timing yourself 6. Calculate your average power 7. Measure time to climb stairs by walking. If possible, use a stop watch for timing yourself 8. Calculate your average power again 9. Compare both average powers and share your observations with your class fellows. How to measure your power output:Sample Chart Assume g = 10 N/kg. How to measure your power output 1. Measure your mass...

2. Measure height of stairs...

... work out your weight

... calculate work done when you climb stairs work = force x distance done = weight x height lifted

3. Measure time taken to climb stairs...

... calculate your average power

power = work done time taken

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Example mass = weight =

40 kg 400 N

height = of stairs work = done =

.3 m

time taken

=

400x3m 1200J

4s

average = 1200 power 4 =

300 W


Teachers’ Guide

Lesson Plans: Physics Typical power outputs

Activity 3 In an attempt to prove that Mr. Ubaid is a very powerful man, he runs up a flight of steps 5.2m high in time of 6.2s. a. Calculate the work done against gravity by Mr. Ubaid if his mass is 80 kg. b. An average person has an average power of about 500 W. Justify, with appropriate working, whether Mr. Ubaid is a powerful man.

Conclusion/Sum up

Assessment

Energy Changed workdone or Power= timetaken timetaken

800 J work done 

To determine your power output in running up a flight of stairs you can measure how much work you do (in joules) when you go upstairs by measuring it by your weight in Newtons (your weight in kilograms x 10). Divide the work you do by the time it takes to do it for find out how much power you exert (in watts) The quicker you go the more power you exert. Faster your work greater is your power

Power is the rate of doing work. Power is calculated using the equation:

Power=

2 s time taken

Land rover engine 65 000 W (65 KW)

small car engine 35 000 W (35KW)

 

washing machine motor 250 W

human engine 400 W

400 w power output

The power consumed or used is said to be one watt if one Joule of work is done in one second. One horse power is the power delivered by a horse as an engine (746 J/Sec) o One horse power is about ¾ kw o One horse power = 746 w

Ask the following questions to assess the students learning:  Draw a table as shown below put in the correct values.

Power (watts)

Time (Sec)

300

5

60 1000 1440

42

Energy transferred (Joule)

30 1000 12


Teachers’ Guide 

Lesson Plans: Physics

The cheetah is the fastest creature on land. A typical cheetah, at full speed, has a power output of 1000 W. Calculate the work done by the cheetah in 1 second and his average power output in 2 seconds.

It is estimated that the human brain has a power requirement of 40 W. How many joules is that per second?  How many watts are there: a. in a kilowatt b. megawatt c. Horse power

Follow-up   

A 100 W lamp is more powerful than 60W lamp explaining this statement. A fat man and thin man ran to the top of hill in the same times. Who is more powerful? Why? Compare personal power developed for running upstairs versus walking upstairs using a stopwatch. Ask students to find out how much power each student can generate.  The students will work in pairs in order to find the time taken for each student to run up a flight of stairs. The stairs used are shown in figure. a. Make a list of all the readings that would be needed. b. Using words, not symbols, write down all equations that would be needed to

43

work out the power of a student. c. Suggest why the total power of the student is greater than the power calculated by this method. Guide the students to solve the problems given at the end of unit of the test book.


Teachers’ Guide

Lesson Plans: Physics

UNIT T O P I C

7

Lesson Plan 9

Pressure/Atmosphere Pressure

Properties of Matter

Grade IX

Students’ Learning Outcomes

The students would explain  Define the term pressure (as force acting normally on unit area).  Explain how pressure varies with force and area in the contact of everyday examples.  Explain that atmosphere exerts a pressure.  Describe how the height of liquid column may he used to measure the atmospheric pressure.  Describe that atmospheric pressure

decreases with the increase in height above the earth's surface. Explain that change in atmospheric pressure in a region may indicate a change in the weather. Information for Teachers

44

Pressure is the ratio of force to the surface area over which it is exerted or it is the effect of a force applied to a surface. Pressure is the


Teachers’ Guide

 

Lesson Plans: Physics

amount of force acting normally per unit surface area. The symbol of pressure is p. normal force pressure = , p= F A area The units of pressure are:

 

1 pascal (Pa) is a pressure of 1 newton per square metre. N  1 Pa  1 2 m 

   

    

The earth is surrounded by an envelope of air called atmosphere. The height of atmosphere is about 300km. Being matter, air exerts thrust or weight on earth surface. One atmospheric pressure is about 1.013x105 Pa. We do not feel such a tremendous pressure because the blood contains dissolved oxygen at a pressure slightly more than atmospheric pressure. Atmospheric pressure decreases with altitude. On high altitude some people fall prey to nose bleeding due to low atomic pressure. Atmospheric pressure is measured with barometer. The miners (worker in mines) face breathing difficulties in the mines below sea level. The atmospheric pressure in mines is very high which causes difficulty in expanding the lungs.

45

Day to day variation in pressure is given by the lines in weather map. All the places with same atmospheric pressure is called isobar. The unit used in weather map is “Bar” and “millibar” Pressure depends on force and area.


Teachers’ Guide 

Lesson Plans: Physics spread the weight over a large area this reduces the pressure. If you wear shoes with very narrow and pointed stiletto heels then you may damage the floor surface and leave a permanent impression or dint. In each of these examples your weight does not change but the pressure under your shoes does.

In north region, the wind moves anticlockwise around the areas of low pressure and clock wise around areas of high pressure. Weather changes as the pressure changes, with low pressure signaling bad weather and high pressure bringing a settled, fine spell. 

Duration/Number of Periods

Encourage students to ask you any questions

80 mins/2 period Material/Resources Required Blackboard, duster, marker/chalks, chart papers, scissors, empty oil cans, beaker, straw, syringe, empty bottle, and balloon

Introduction

that they might have on the topic.

Brainstorm with students about force and pressure

Ask students, why a needle will go through a piece of cloth, but with the same amount of force, a pencil will not?

After getting responses from students tell them that the differently shaped points of the needle and pencil exert different amounts of pressure.

Ask the students what is the difference between force and pressure?

Explain to them when a force acts on an object it exerts pressure. Pressure acts at right angle to the object itself, and its strength depends on the amount of force and the area over which it is applied. Someone walking on soft snow will sink into it in normal shoes but not if they wear snow shows or skis. The person's weight is the same but snow shoes

Ask students do they know about the atmosphere

Share the following information about atmosphere and atmospheric pressure with students.  Because we have spent all of our lives living in the atmosphere of the Earth, we seldom think that we have 20 km or so of air pressing on us. We do not feel the pressure because it does not just push down, it pushes us inwards from all sides. Our lungs do not collapse, because the same air pressure flows into our lungs and presses outwards.  Ask to students what would happen if our lungs did not contain any air and there was vacuum inside them.

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Teachers’ Guide

Lesson Plans: Physics pressure is now much greater than the pressure inside the can, so it crushes the can and makes it volume very small.

Development Activity 1 

Demonstrate some effect of air pressure.

Divide the class in groups of five to seven students each.

Assign to each group one of the following investigations  The can crashing experiment  The milk bottle experiment  Sucking  The syringe

Guide them to record their observations on their observation sheet and find their inferences.

Call on a volunteer from each group to share group finding with the whole class.  G ro u p 1 : T h e ca n c ra s h i n g experiment  Instructions: o Put a small volume of water in a metal can and boil the water for several minutes to drive out most of the air (Figure a). o Stop heating and immediately seal the can with a well-fitting rubber stopper. o At the moment you close the can the steam pressure inside exactly balances the atmospheric pressure outside o As heat is lost from the can the steam inside condenses and the inside pressure falls. (Expected inferen ce: T h e at mo s p h eric

Group 2: The milk bottle experiment  Instructions: o Fill a milk bottle full of water by immersing it in a bowl of water. o Keeping the top of the bottle below the water surface, lift the rest of the bottle out of the water. 

The water does not run out of the bottle. Why? (Expected result: The atmospheric pressure P1 (or air pressure) on the surface of the water balances the pressure of the water P2 inside the bottle. If the water began to run out of the bottle then, without any air in the bottle P2 would become less than P1. The atmospheric pressure will not allow this to happen).

o

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Teachers’ Guide

Lesson Plans: Physics

Group 3: Sucking  Instructions o We think of sucking a drink up a straw as being a result of our action rather than an effect of atmospheric pressure. o Try sucking a drink up a straw from an open-topped glass and you will be successful (a). o Try sucking the drink out of the bottle with the closed top (b). 

  o

o

o

o

As there is no air inside this bottle and no access for atmospheric pressure, you will not successes in sucking up much of this drink. Why? (Expected reasoning: When you suck you increase the volume of your lungs, which reduces the air pressure inside your lungs and your mouth. The atmospheric pressure acting on the surface of the liquid is now greater than the reduced air pressure inside your mouth, so drink is pushed up the straw by the pressure excess of the atmosphere over your mouth pressure. The absence of atmospheric pressure on the surface of the liquid in the closed bottle means that there is no excess pressure to push the liquid up

o

the straw). Group 4: The syringe Instructions A syringe has a piston which slides smoothly inside a cylinder making an airtight seal. To fill a syringe, start with the piston at the bottom of the cylinder. Place the nozzle below the liquid surface and pull the piston upwards. This produces a low pressure in the cylinder below the piston. How a syringe works? (Expected inference: The greater atmospheric pressure on the surface of the liquid pushes it up the nozzle into the cylinder. When the syringe is removed from the liquid, as air is unable to get back into the cylinder below the piston, the atmospheric pressure at the opening of the nozzle helps to keep the liquid inside). When the syringe is used the piston is pushed down the cylinder applying increase pressure to the liquid and forcing it out of the nozzle against the atmospheric pressure.

Activity 2 

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Instructs the students to follow the following steps to make a homemade barometer capable of measuring changes in air pressure.


Teachers’ Guide

Lesson Plans: Physics Step 1

Step 4

Cut a large part of balloon and stretches it tightly over the jar opening .Use a rubber band to hold at fast

Fasten a file card to the wall place the barometer by it. Have the straw pointer centered on the card and almost touching

Make a mark on the card, where the straw points each day.

Explain the working of the barometer in the following day  Increased air pressure pushes down harder on the balloon diaphragm. This makes the straw pointer go up. Decreased air pressure caused the higher air pressure inside the jar to push up on the diaphragm so the pointer goes down.

Only thing that can affect the proper working of this barometer are the rapid temperature changes. Place this kind of barometer at the place, where it will have the least changes of temperature otherwise the air in the jar may expand and contract so much that the effects of changing air pressure will be obscured.

Ask the following questions to students to complete their observations: a. On what day was the air pressure highest? b. On what day was the air pressure

Step 2 Pinch one straw end flat and cut a point with scissors at this end

Step 3 Glue the straw other end to the centre of the stretched balloon

49


Teachers’ Guide

Lesson Plans: Physics

lowest? c. When, if at all, were there no changes in the air pressure? 

in the atmosphere. There are two main types of barometers – the most widely available and reliable Mercury Barometers, or the newer digital friendly Aneroid Barometer. How does a Barometer Work?  The classic mercury barometer is typically a glass tube about 3 feet high with one end open and the other end sealed. The tube is filled with mercury. This glass tube sits upside down in a container, called the reservoir, which also contains mercury. The mercury level in the glass tube falls, creating a vacuum at the top.  The barometer works by balancing the weight of mercury in the glass tube against the atmospheric pressure just like a set of scales. If the weight of mercury is less than the atmospheric pressure, the mercury level in the glass tube rises. If the weight of mercury is more than the atmospheric pressure, the mercury level falls.  Atmospheric pressure is basically the weight of air in the atmosphere above the reservoir, so the level of mercury continues to change until the weight of mercury in the glass tube is exactly equal to the weight of air above the reservoir.  In areas of low pressure, air is rising away from the surface of the earth more quickly than it can be replaced by air flowing in from surrounding areas. This reduces the weight of air above the reservoir so the mercury level drops to a lower level.  In contrast, in areas of high pressure, air is sinking toward the surface of the earth more quickly than it can flow out

Asks the students to note the air pressure by this barometer everyday they come to school sharp at 8:00 o'clock for six consecutive days and plot a graph showing changes in air pressure.

Activity 3 

Explain the working of the mercury barometer with the help of a chart.

Ask the students what do you see in the picture (Mercury Barometer)

Share the following information about the height of liquid column used to measure the atmospheric pressure.

Encourage students to ask you any questions that they might have

What Is a Barometer? A barometer is a widely used weather instrument that measures atmospheric pressure (also known as air pressure or barometric pressure) - the weight of the air

50


Teachers’ Guide

Lesson Plans: Physics

to surrounding areas. There is more air above the reservoir, so the weight of air is higher and the mercury rises to a higher level to balance things out 

Pressure = (density of mercury) x (acceleration due to gravity) x (height of the mercury column) = 13590x9.81x0.760 Pascal = 101300 Pascal So the standard atmospheric pressure is 760 mm of Hg and 1 atmosphere pressure is equal to 101300 Pascal.

Activity 4 Shows the following picture of the weather map to the students and ask how the weather is estimated? (Expected responses from the students)  Weather map usually represents the information about atmospheric pressure at sea level  Weather changes as the pressure changes, with low pressure signaling bad weather and high pressure brining a settled, fine weather.  Heavy rains and strong winds are brought by low atmospheric pressure.

Some barometers have a tube containing a column of mercury that moves with changing pressure. The higher the pressure, the farther the mercury rises in the tube. Standard Atmospheric Pressure  Call on a volunteer to do the following calculations on the black board to calculate the standard atmospheric pressure.  A pressure of 760 mm of Hg is known as standard atmospheric pressure or 1 atm. Its value in Pascal can be calculated as by estimating the pressure at the bottom of the mercury column 760 mm high  The density of the mercury is 13590 kg/cubic meter  Acceleration due to gravity is 9.81 Newton/ kg  The height of the mercury column is 0. 760 meters Then

Conclusion/Sum up 

51

We live at the bottom of a deep ocean of air called the atmosphere. It may be look not very dense, but it exerts a very high pressure. In some ways, the atmosphere is like a liquid.


Teachers’ Guide

Lesson Plans: Physics

it pressure acts in all direction and become less as we rise up through it .Unlike a liquid however the atmosphere pressure is very high at the lower Levels since the atmosphere is much dense at lower levels. Down at in sea level, the air pressure is about 100,000 Pascal (100,000N/m2) equivalents to the weight of 10 cars pressing on each square meter. We are not crushed by the atmospheric pressure, since the pressure in our blood system is more than enough to balance it. Our ears are very sensitive to changes in pressure when we travel up a hill quickly in a car, the outside air pressure drops as we rise up through the atmosphere and we experience a popping sensation in our ears. Some useful application of a pressure difference.

Assessment Explain: 

Why it is difficult to remove the lid from a preserving jar which was closed when the space above the food was full of steam.

Why evaporated milk flows out of a can more easily if two holes are made at opposite sides of the can top.

Why dams which hold water in reservoirs must be much thicker at the base of the dam than at the top.

Why high-flying aircraft need to be airtight and have pressurized cabins for the people.

Change in atmospheric pressure in a region may indicate a change in the weather.

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Teachers’ Guide

Lesson Plans: Physics Follow-up

  

Prepare flash cards showing, “How atmospheric pressure manifests itself in everyday life physical phenomenon of nature?” Discuss these cards in class room seminar. Use a homemade barometer to estimate the atmospheric pressure for one month and compare its reading with the standard weather report on the air pressure in your area. Explain how squeezing and releasing the bulb of the drooping pipette will fill that pipette.

dropping pipette

Investigate how a fire extinguisher works.

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Teachers’ Guide

Lesson Plans: Physics

UNIT T O P I C

14

Electric Power & Joule's Law

Current Electricity

Grade X

Information for Teachers

Students’ Learning Outcomes

  

Lesson Plan 10

Describe how energy is dissipated in a resistance and explain Joule's law. 2 Apply the equation E = IVt = I2Rt = V t R to solve numerical problems Calculate the cost of energy when given the cost per KWh.

 

Duration/Number of Period

40 mins/1 period

54

Electrical energy is converted into the internal energy of a conductor which results in the rise of temperature. If the heat produced is sufficiently high, the wire may glow and give off light. In the filament bulbs, the rise in temperature is so large that they start emitting light. The P.d is the energy or work done per unit charge in displacing it from one point to the other.


Teachers’ Guide

P.d = V = 

   

 

W = QV

- (i)

Cost =

P(in watts) x t(in hr) x No. of days x cost of one unit 1000

The current is the rate of flow charge i.e.,

I = Q/t 

W Q

Lesson Plans: Physics

Q = It

Material/Resources Required

- (ii)

According to Ohm's law. V = IR - (iii) Using value of Q & V in eq (i) Energy transfered = w = It x IR = I2Rt The conclusion was reached by Joule & Lenz working independently and is known as Joul's law. The electrical energy is measured with joule meter (electric meter) The commercial unit of electrical energy is KWh. KWh is the energy supplied/consumed for one hour at the rate of 1000 watts. In practical application the units of power used are kilowatt (KW) Megawatt (MW) and horse power (hP). 1 KW = 1000 w 1 MW = 106w 1 hP = 746w Power is the rate at which electrical energy is transferred (from place to place) or transformed (from one form to another). Energy transferred (J) Power (W)= time (s)

Bulb, battery, connecting wire, bulb holder, textbook X etc.

or Energy transferred (J) = Power (W) x Time (s) To find the cost of energy, it is more convenient to calculate the total energy in kwh. Cost = number of kilowatt-hours x price per kilowatts hours. The voltage of an electrical appliance is usually the same as that of domestic main supply. In Pakistan the voltage of electrical supply is 220V. The cost of electrical consumption is given as

55

Introduction Activity Construct a circuit in class room by using connected wire, cell and blub. Ask students to observe it. conventional current

battery conducting wire filament bulb

Ask the following questions to recall from the students: Q1: What energy changes take place when we switch on the bulb? Ans: Electrical energy is converted into the internal energy of the Filament of the bulb which results in the rise of temperature. In case of the filament of the bulbs, the rise in temperature is so large that they start emitting light. Q2: What energy changes take place when we switch on the heater? Ans: When the electricity is passed through the element of the heater


Teachers’ Guide

Q3: Ans: Q4:

Ans:

Q5: Ans: Q6: Ans:

Lesson Plans: Physics What is Ohm's Law?  According to Ohm's law - The current flowing through a metal conductor is directly proportional to the potential difference across its ends provided the temperature and the other physical conditions remain the constant. Mathematically we can write V = IR - (iii) What is Joule's law for the energy dissipation in resistors? Using value of Q & V in eq (i) Energy dissipated = w = It x IR= I2Rt The conclusion was reached by Joule & Lenz working independently and is known as Joule's law. What is power in an electrical circuit? When current flows through a resistor, all the potential energy lost by the charges is changed into heat. In many circuits it is important to know the rate at which such energy changes take place. When energy changes from one form to another, the power indicates the rate at which the change is taking place. Power=energy transferred/time If energy is measured in joules (J) and time in seconds (s), then power is measured in joules/second or Watts Units for the measurement of power in an electrical circuit In practical application the units of power used are kilowatt (kw) megawatt (Mw) and horse power (hP) 1 kw = 1000 w = 103w 1 Mw = 106w 1 hP = 746w Formula for the calculation of the cost of electrical consumption  The cost of electrical consumption is given as

(NICROME WIRE) , the electrical energy is changed into the heat energy . What relation we can use to calculate the power dissipated? Power is equal to the square of the voltage divided by resistance. What is the relation between power dissipated and the resistance of the heating element? The lower is the resistance of the heating element, the greater is the power dissipated What is the unit for the measurement of the power? Power is measured in joules per second or watts. What are the other units for the measurement of power? Larger powers are measured in Kw: 1Kw=1000 watts

Development Activity 1 With the help of students perform the following calculations on the black board and explain to the students. What is the potential difference? The potential difference (P.d) between two points in a circuit is the work done per unit charge in displacing it from one point to the other. P.d = V = W Q

W = QV

- (i)

What is electric current?  The current is the rate of flow of the electrical charge i.e.,  I = Q/t Q = It - (ii)

56


Teachers’ Guide

Lesson Plans: Physics

Cost = Power (in watts) x time (in hours) x No. of days x cost of one unit (kWh) 1000 Activity 2 Teacher asks the students to carry out an extensive survey of electrical appliances at their homes. In their survey they collect the information and complete the given table. If cost of one electrical energy unit = Rs.5 Appliances

No. of Appliances

Power Rating

Estimated Usage (hour per day)

Energy Consumed

Cost of Energy

Average Monthly Electric Bill

Bulb Fan T.V Total

Activity 3 Hang the following information sheet in the class on the board and ask the following question to the students: Q1: What is the standard voltage supply in Pakistan? Ans: 220 volts Q2: What is the standard voltage at which all the electrical appliances work properly? Ans: 220 volts Q3: Which appliance use, the highest electrical energy? Ans: Electric Oven Q4: Which appliances should be used at the minimum to reduce monthly bill? Ans: Electric oven, Electric heater, geyser and electric kettle

57

Appliances

Power Voltage Rating of Rating of Appliances Appliances (in w) in Volt 15 – 200

220

Tube Light

40

220

Electric Fan

60 – 100

220

T.V

120

220

Electric Iron

750

220

Room Heater

1000

220

Geyser

1500

220

Electric Kettle

2000

220

Electric Oven

3000

220

Bulb


Teachers’ Guide

Lesson Plans: Physics

Activity 4 Conclusion/Sum up

Give following word problems to students to solve.  Help them where needed. (1) In a certain house, 4 electric bulbs of 100W each, and daily used for 5 hours. If the rate of electricity is Rs. 4 per unit, find the number of units consumed in 30 days and what would be its cost? Solution: Step 1: The number of units consumed = watt x time of use (in hours)/1000 = 4 x 30 days x 5h x 100w/1000 60kWh = 60units Step 2: Total Cost = number of units consumed x cost of one unit = 60 x 4 = Rs. 240/(2) A student uses two 150w lamps for 6 hours. If the price per unit of electricity is Rs. 10 what is the cost of this? Step 1: Calculate the power being used, in kW: Power=2 x 150 W = 300 W = 0.3 kW Step 2: Calculate the energy transferred, in kWh: Energy transferred = power x time = 0.3kW x 6h = 1.8kWh Step 3: Calculate the cost: Cost = number of kilowatt-hors x price per unit =1.8kWh x 10 = 18 Rs. 

Electric current

Effects of Current

Chemical Effect i.e electroplating

Heating Effect Heat energy Light energy

which consumes power and energy given by

P = IV where P = power (W) I = current (A) V = potential difference (V) E = Pt where E = energy (J) P = power (W) t = time (s)

used in finding the cost of electricity consumption in

Kilowatt-hours (kWh) or residential units of electricity

58

can cause electric shocks or fires in situations such as

Damaged insulation  Overheating of cables  Damp conditions 

which can be prevented by using

Safety measures

Magnetic Effect i.e Door bell


Teachers’ Guide

Lesson Plans: Physics ( c) Electric irons

Assessment Q1:

A manufacturer uses substandard wires in the windings of the electric motors. This reduces its cost. Is it advisable? Ans: No, the cost of the electrical energy consumed would be increased Q1: How does the heating effect depend upon current? Ans: Amount of heat energy increases on passing more current Q1: How many 60 w lamps operated at 220V can be switched on at the same time if there is a 5A fuse in the lighting circuit? Ans: No. of Bulb s x power of one bulb = V x I n x P = VI n x 60 = 220 x 5 n = 220 x 5 60 = 18.6 No. of bulbs should not exceed 18 otherwise fuse will blow. Q1: Enlist energy changes which can be observed as electric current is passed through each of the following appliances? Appliances

Energy Changes

Electrical energy is converted to heat energy.

Q:

Make recommendations to reduce your electric consumption. Ans: Actions that can reduce the electricity bill:  Turn off all the unnecessary lights. Develop a habit to turn off the bulbs every time you go out of the room.  Use laptop instead of the desktop computer  Minimize the use of the air conditioners, electric iron electric heater, washing machine etc.  Try to dry out your clothes in the sun light instead of using dryer of the washing machine.  Do not operate the electrical appliances on stand by , just turn them off.  Try to make maximum use of sun light in homes and offices.  Operate air-conditioner at 26 degrees.  Try to use quality controlled certified cables in your wiring systems.  Use energy savers instead of ordinary bulbs.  Raise the interior temperature of your freezer and refrigerator.  Solar garden lights should be used in place of those connected to the home's electrical outlets.  Table lamps should be used instead of ceiling lights when reading a book.

(a) Electric Heater (b) Electric Lamps

Follow-up

( c) Electric irons Expected Answers Appliances (a) Electric Heater (b) Electric Lamps

Energy Changes

Ask the students to design a poster indicating therein strategies to minimize energy consumption after discussing as a whole group, share ideas and problems.

Electrical energy is converted to heat energy. Electrical energy is converted to heat and light energy.

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Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 11

T O P I C

14

Alternating Current (A.C), Safety Measures Current Electricity

Students’ Learning Outcomes

Grade X

Information for Teachers

The students will:  Distinguish between D.C. and A.C.  State the functions of live, neutral and earth wires in the domestic main supply.  Describe hazards of electricity (damage insulation, overheating of cables, damp conditions)  Explain the use of safety measures in household electricity (fuse, circuit breaker, earth wire).

 

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The current which is steady and does not vary with time is called direct current (DC). Cells and batteries supply D.C.


Teachers’ Guide 

 

 

Lesson Plans: Physics

The current which continuously changes in strength and reverses its direction many times in a second is called A.C. A fuse is a safety device/wire and is the weakest point in an electrical circuit. Fuse melts and breaks the electric circuit when the circuit gets overheated with large withdrawal of current due to short circuiting or due to power fluctuation. A fuse has low melting point. Fuse made from 50% of tin and 50% of lead melts at 200oC. Fuse has high resistivity. Thicker is the fuse wire, more is the current needed to melt it. These are normally rated at 1A, 2A, 3A, 5A, 10A and 13A. Its rating is slightly more than the current flowing through the appliances. The color of the wires used in an electrical circuit are: Live – Brown Neutral – Blue Earth – Green/yellow Earth wire is a low resistance wire connected to the metal casing of the appliances. It protects from electric shock. Large amount of current produces greater amount of heat which may damage the conducting wire. This is called overheating. When live wire gets contacted with the neutral wire the circuit is called short circuit. Human body can withstand only a current of 50mA. The resistance of the body is very low hence large electric current cause an electric shock and even death. While changing the fuse, switch off the mains.

Material/Resources Required Connecting wires, bulbs, switch, fuses and batteries

Duration/Number of Periods 40 mins/1 period

61

Introduction Activity Asks and discuss the following questions from the students Questions

No.

Answers

1

How the light is produced in the electrical lamp ?

2

How the heat energy is produced Electricity change into in the electric heater? heat energy

Due to current

Development Activity 1 Show the two pin plugs and three pin plugs to the students and explains the functions of live wire, neutral wire and the earth wire to the students


Teachers’ Guide

Lesson Plans: Physics Activity 3

Informs the students that Power plugs have to be wired according to the international color code.  The blue wire is the neutral conductor and it conducts electricity from the appliance to the power source.  The brown wire is the live conductor and conducts electricity from the power source to the appliance.  The yellow-and-green wire is the earth wire and it conducts excess electricity away when there is a short circuit.

Show the following symbol to the students and asks them the following questions:

Have you ever seen this sign? (Yes, No) What does it mean? (Danger) Why is it exhibited at electricity plants? ( To make them inform)

Activity 2 Ask the students to use the appropriate color to indicate how they would wire the power plug in the following sketch:

Activity 4 Tell the students to go the library and search out the safety measure for safe working with electricity and then prepare a chart and hang it in the class room Electricity is dangerous. Remember the following safety measures when you work with electricity:  Never try to repair a broken electrical appliance yourself. Rather ask a trained electrician to do the job.  Water is a good conductor of electricity. Never work with electricity when you are near water.  Do not pull a power plug from the socket by the cord.  Ensure that you know where the building's main switch is so that you will be able to switch off the main stream immediately if something should go wrong.  Do not install electrical cords underneath carpets. It is too difficult to check the condition of the cord if it is not visible at all times.  It is good policy to get a qualified electrician to check electrical appliances from time to time

Asks the students to investigate do some research on Internet or consult some lab manual to find out “why it is important to have an earth wire while operating a kettle?” The earth wire is a safety wire which connects the metal body of the kettle to the earth and prevents it from becoming live if a fault develops. If for example, the live wire to work loose and touch the body of the kettle, a current would immediately flow to the earth and blow the fuse. If there were no earth wire, the body of the kettle would remain live and a possible lethal current would flow through the anyone who happened to touch it

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Teachers’ Guide

Lesson Plans: Physics

Activity 5 By showing the pictures of fuse and circuit breaker and also ask the following question Q1. What is fuse? Ans. A fuse interrupts excessive current (blows) so that further damage by overheating or fire is prevented. Fuses are selected to allow passage of normal current plus a marginal percentage and to allow excessive current only for short periods. Q2. How the fuse is placed in the circuit? Ans. Like the switch, it is placed in the live wire often in the form of small cartridge inside the plug Q3. How the fuse works? Ans. If too high current flows in the circuit, the fuse blows and breaks the circuit before the cable can overheat and catch fire Q4. What is a circuit breaker? ans:. A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Q5. How the fuse is different from the circuit breaker? Ans. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation

Conclusion/Sum up 

There are three wires in the electrical supply to a house. The blue wire is the neutral conductor and it conducts electricity from the appliance to the power source. The brown wire is the live conductor and conducts electricity from the power source to the appliance. The yellow-and-green wire is the earth wire and it conducts excess electricity away when there is a short circuit Fuse and circuit breaker protect fixed insulation cables from overheating and possible fire risk. Earth wire protects the user from electric shocks. Damped condition may be fatal for human beings. Assessment

Ask the following questing to assess the students learning.  Explain why, for safety, you should disconnect the battery before working on a car engine.  Explain why do should not:  Fly kites near overhead cables?  Connect to many appliances to one socket?  Leave a television set plugged in overnight? Follow-up 1. Class quiz on electricity related hazards

topics. 2. Ask the students to make three posters on

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Teachers’ Guide

Lesson Plans: Physics

common electrical hazards and display the posters on main notice board of the school.

Sample Poster for Teachers Switch off all heating appliances if the power fails. Fires have been caused when power returns unexpectedly.

Wear dry leather gloves when welding. Touching the electrode can be dangerous because of the voltage present.

Switch off before pulling out a plug.

Tie the tapes of the electric blanket to prevent creasing.

Grasp the plug

not the cord.

Don’t spray household cleaners and insecticides on power points or switches. They may cause cracking and an electrical hazard.

Teach children that power points and appliances are not toys. Children can touch live pins of plugs. Plastic covers for power points reduce the chance of children inserting objects.

Combustible material must be kept clear of all heating appliances, such as bedding, clothes, curtains, furniture, newspapers, etc.

Some ov erseas products may not operate satisfactorily or safely because of at 240V, 50Hz supply. Such products could not be used without modification. Have them checked before use.

3. Find out why:  bathroom lights have to be switched on and off by a pull-cord;  extension leads shouldn’t be coiled up tightly when in use;  electric drills and food mixers are double insulated.

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Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 12

T O P I C

15

Force on a current carrying conductor in a magnetic field

Electromagnetism

Grade X

Students’ Learning Outcomes

The students will: 

Explain by describing an experiment that an electric current in a current carrying conductor produces a magnetic field around it

Describe the application of the magnetic effect of an electric current in relay, door latch, loud speaker and a circuit breaker

Information for Teachers

Conduct an experiment to identify the pattern of magnetic field of a (1)permanent magnet (2) straight Current carrying conductor (3) circular coil carrying current using iron fillings and a magnetic compass

1. Magnetic Fields are not the only source of a

Magnet. Tests with iron fillings and a plotting compass show that a wire has a magnetic field around it whenever a current is passed

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Teachers’ Guide

Lesson Plans: Physics

through it  Right hand rule is used to find out the direction of the magnetic field produced around a straight current carrying conductor .This rule states, “If the thumb of the right hand points in the direction of the conventional current in the wire then fingers encircle the wire in the direction of the magnetic field lies” 2. If the current is passing through a loop of wire or a coil, then again the magnetic field is developed, outside the coil, the field lines run in the loops from one face of the coil to the other. The field is similar to that produced by a short bar magnet and the coil acts as if it has a north pole on one face and a south pole on the other. Right hand grip rule is used to find out which of the two faces is the North Pole. 3. When the current is passed through the solenoid, each turn acts as a single coil and produces a magnetic field. All the turns in a combined way give rise o a magnetic field that is similar to the field around a long bar magnet and the coil behaves as if it has a north pole at one end and a south pole at the other. The poles of the magnet thus produced can be determined by the Right Hand Grip Rule that states, “Imagine your right hand is gripping the coil in such a way that your fingers are curled in the direction of the conventional current flow, then the extended thumb points in the direction of North Pole” 4. Electromagnets are widely used as components of other electrical devices, such as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments, and industrial lifting electromagnets for picking up and moving heavy iron objects like scrap iron. The discovery of electromagnetism has played a vital role in developing the present day technology oriented society.

Duration/Number of Periods 120 mins/3 period Material/Resources Required Compass needle, metallic conductor in the form of strip or wire, battery, power supply, Iron stand, switch

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Introduction Activity 1 Provide the bar magnets, iron fillings and compass needles to the students in groups and ask them to draw the magnetic field of the permanent bar magnet by passing following instructions (students already know to draw magnetic field of the bar magnet using compass needle)  Fix a sheet of paper on a drawing board  Place a bar magnet on the sheet of paper  Trace the boundary NS of the bar magnet  Place a compass at the North Pole  The magnetic needle comes to rest in a particular direction  Mark the ends of the needle. The tail end of the needle is the south pole and the tip of the needle is the north pole  Now move the magnetic needle in such a way that its tail (south pole) always points towards the north pole of the bar magnet  Mark the new position of its north pole  Repeat this until you reach the other end of the magnet  Join the points


Teachers’ Guide   

Lesson Plans: Physics

These points form a curve The curved line represents a magnetic field line or magnetic line of force Repeat the above procedure and draw as many lines as you can

Activity 2 Asks the students to set up the electric circuit according to the following circuit diagram using connecting wires, battery cells, plotting compass, variable resistance switch etc 

Ask the students to pass an electric current through the circuit by closing the switch and make the following observations. Sr. No Activity performance Place a plotting compass above the wire XY at 1 position A and note what happens? Place a plotting compass 2 below the wire as in position B?

Expected Observation Expected Inference It would deflect and settle to a Presence of magnetic point to the east as in the field position A It would point in the west Presence of magnetic field in the reverse direction direction

Development Activity 1 

Ask the students to use connecting wires, copper wire AB, a piece of card board, compass needle, ammeter, rheostat, iron fillings, battery and a switch to set up a simple circuit to observe the magnetic field around a straight current carrying wire. Ask the students to perform the activity step by step as is mentioned in the procedure and to note down the observations and draw the corresponding inferences after group discussion.

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Teachers’ Guide

No.

1.

2.

3.

4.

5.

Activity performance Arrange a copper wire AB, ammeter, compass needle, battery and a thick sheet of cardboard with a hole at its centre as shown above–keep the switch open in this case Sprinkle some iron filings on the cardboard and Gently tap the cardboard Now switch on the current in the circuit and gently tap the iron fillings

Increase the magnitude of current in the circuit using a rheostat

Switch on the current in the circuit and tap the card board sheet. Use the plotting compass to find out the direction of the magnetic field

Lesson Plans: Physics

Expected Observation Circuit is set up as per circuit diagram

The iron filings do not show any change in their arrangement because no current is flowing through the conductor The iron fillings rearrange themselves in concentric circles with copper wire at the centre

Expected Inference Circuit is an open circuit

In the absence of any current in the circuit, the iron fillings do no rearrange themselves in some specific pattern The rearrangement of iron filling in concentric circles shows the presence of magnetic field around the wire The iron fillings’ response The strength of the to rearrange them in magnetic field produced concentric circles is more due to flow of current in pronounced than in the the wire AB is directly previous case proportional to electric current The concentric circles are When the current is representing the flowing from top to the magnetic field and the bottom of the copper wire magnetic field direction is AB then the direction of clockwise–the current in magnetic field is clock wise the copper wire AB is from top to the bottom

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Teachers’ Guide Reverse the direction of the current in the circuit and Use the plotting 6. compass to find out the direction of the magnetic field Now imagine that you are holding the current carrying conductor in your right hand in such a way that thumbs points in the direction of the current, then note down the 7. direction in which the fingers of your hand are curled

Lesson Plans: Physics By reversing the current in the circuit , the magnetic field direction comes out to be anti clockwise–the current in the copper wire is now from bottom to the top The current is flowing from bottom to the top of the copper wire Thumb is pointing in the direction of the current The fingers are curled in the direction of magnetic field that is in the anti clock wise direction

When the current is flowing from the bottom to the top of the copper wire AB then the direction of the magnetic field is anti clockwise If we hold the current carrying conductor in our right hand in such a way that thumb points in the direction of the current then the direction in which the fingers are curled is the direction of magnetic field produced - Famous right hand rule for determination of the direction of magnetic field around a straight current carrying conductor

Activity 2  

   

Divide the class into groups to perform the laboratory work. Give instructions to the students to set up apparatus as shown in the circuit diagram given below to investigate the magnetic field produced due to flow of the electric current in the circular loop of wire. Ask the students to take a long wire and bend it to form a circle. Ask them to pass the wire through the cardboard such that half the wire is above it and the remaining part of the wire is below the cardboard. Instruct them to join the free ends of the wire to the battery through a plug key. Ask them to perform the experiment step by step as shown in the table below and to record their observations to draw inferences.

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Teachers’ Guide No.

Activity performance Set up the circuit as 1. shown in the circuit diagram Sprinkle some iron filings on the cardboard 2. and Gently tap the cardboard Now switch on the current in the circuit and gently tap the iron fillings 3.

Lesson Plans: Physics Observation Circuit is set up as per circuit diagram

Inference Circuit is an open circuit

The iron filings do not show any change in their arrangement because no current is flowing through coil

In the absence of any current in the circuit the iron fillings do no rearrange themselves in some specific pattern

 

Circular pattern is around the points where the wire passes through the cardboard The pattern near the centre of the loop is almost straight. The concentric circles become larger as we move away from the wire

Use a plotting compass to trace the magnetic field 4.

What result you can infer while carefully observing the pattern of magnetic lines of force

Concentric circles are formed, which are centered at the points where the wire passes through the cardboard  The lines near the centre of the loop are almost straight. 5. The magnetic field at the centre of the loop is perpendicular to the plane of the loop  The concentric circles become larger as we move away from the wire Increase the The iron fillings’ response to magnitude of current rearrange them in concentric in the circuit using a circles is more pronounced than in 6. rheostat the previous case. The number of the concentric circles increases with increase in the current 

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The rearrangement of iron filling in concentric circles shows the presence of magnetic field

The field is traced and direction of the current flow in the loop of wire is noted. It is noticed that magnetic field at centre of the loop is perpendicular to the plane containing the loop One face of the loop is behaving as south pole and other is behaving as north pole

The strength of the magnetic field produced due to flow of current in the loop is directly proportional to electric current strength


Teachers’ Guide Now reverse the direction of the current in the circuit and use the plotting compass to find out 7. the direction of the new magnetic field lies Now imagine that you are holding the current carrying loop of wire in your right hand in such a way that the fingers are curled in the direction of the flow of the current in the loop then find out 8. the nature of the pole on the face of the loop in the direction in which the thumb points out by using a compass needle or by bringing a freely suspended bar magnet close to the loop

Lesson Plans: Physics The magnetic field reverses its direction

The direction of the magnetic field is reversed when this direction of flow of the current in the circuit is changed.

When the fingers are curled in the direction of flow of the current in the wire ,then thumb points out in the direction of the north pole of the short disk magnet that produces the same magnetic field as that of loop of wire at its centre when a current is passed through it

When the fingers of the right hand are curled in the direction of the flow of the current in the circular loop of wire , then thumb points in the direction of the north pole of the magnet that produces the same magnetic field as that of the circular loop of wire at its centre due to flow of the current – famous right hand grip rule The loop of wire acts as if it has a north pole on one face and a south pole on the other.

Activity 3

Activity 4

Show the following picture to the students and ask them to describe, “How the magnetic field of a coil is identical to the field of a disk shaped permanent magnet”

Ask the following questions from the students What is the function of an electrical switch in a circuit? (It is used to make electricity to flow in the circuit and to stop it to flow in a circuit when desired) What is the use of loud speakers in everyday life? (Loud speakers are used to magnify the sound effects)

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Teachers’ Guide

Lesson Plans: Physics

Where the loud speakers are mostly used? (Loud speakers are mostly used in mosques, with computers and in radios etc) What is the function of a circuit breaker? (Under predetermined designed conditions, it stops the flow of electric current in the circuit) What is main purpose of putting locks on doors? (To provide security to the assets) After getting responses from the students provide the circuit diagrams of the following instruments that operate by making use of electromagnet and explain their mode of working. 

Electric relay

Loud speaker

Magnetic circuit breaker

the circuit therefore no magnetic attraction exists over the small metal “coin” ( we call armature ), the relay contact on the left is still open , no current flows through the yellow battery  When the blue battery is connected, current flows through the coil and a magnetic field is produced in, the iron core/nucleus placed along the axis of the coil. The magnetic field produced attracts the armature and it is pulled against the nucleus, closing the relay contacts at the left. This action completes the electric circuit and the yellow battery current flows through the lamp, lightening it.  When the blue battery current is interrupted , coil stops to generate the magnetic field , the armature becomes free the and the spring effect of the contact arm pushes it up , opening the contact , turning off the yellow battery current and the lamp Circuit diagram # 2

 Magnetic door latch Circuit diagram #1 Electric Relay

Loud speaker

 

A relay is a switch which is operated by the electromagnet. When the blue battery is disconnected from the electric coil, no current flows in

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Teachers’ Guide

Lesson Plans: Physics

A loud speaker has a permanent magnet and a electromagnet.  To make sound waves in the air, the paper cone must be made to vibrate back and forth  The current flowing in the coil is the alternating current supplied by the amplifier. , it flows back and forth in the wire of the electromagnet coil. Its oscillations are the electric version of the sound waves that the listener wants to hear.  The current flows one way around the coil, turning it into a magnet .One end is the north p[ole and the other end is the south pole . When the current changes direction. the poles reverse  The permanent magnet has unchanging poles. , north at one end and south at the other end. When the current flows one way through the coil, it is attracted by the permanent magnet, when the current reverses, it is repelled.  This means the coil is pushed back and forth. It is attached to the paper cone , so the cone also moves back and forth  The cone pushes the air, sending oscillations to the listener's ears. these oscillations are sound waves Circuit diagram # 3 

This uses an electromagnet. If the current exceeds the rating of the circuitbreaker the pulling force of the electromagnet attracts an iron latch which breaks the electrical contacts.

The 'springy piece of metal' acts as a catch to reset the switch. The force of attraction between the iron rocker and the electromagnet has to be large enough to overcome the spring catch. Once the iron rocker has been moved down on the left hand side of the pivot the side on the right is pushed past the catch Circuit diagram # 4 

Magnetic circuit breaker 1. Magnetic latches /magnetic locks use

electromagnetism to control the locking mechanism. They rely on electricity, either through the construction of the current or the battery. 2. The core of a magnetic locking system is a solenoid in advanced metal alloys. When electricity activates, the bolt

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Teachers’ Guide

Lesson Plans: Physics

slides in and out, up or down along its Ushaped channel to lock or unlock the door. 3. Some magnetic locks also include synchronization mechanisms that allow them to operate only at certain times – during working hours, for example. Others have “transaction memory” which records each use or attempted use. 4. This can be particularly useful with locks that use the number pad instead coded cards: if an unauthorized person tries to access using incorrect codes more than twice, for example, the automatic locking triggers an alarm.

Conclusion/Sum up 

A magnetic field always exists around a straight current carrying conductor in the form of concentric circles with conductor at the centre. The magnetic field lasts as long as the current is passing through the wire.

straight current carrying conductor is determined by the right hand rule that states, “If the thumb of the right hand points in the direction of the conventional current in the wire then fingers encircle the wire in the direction of the magnetic field. The magnetic field pattern produced by a current flowing in a circular loop of wire shows that outside the coil, the field lines run in the loops from one face of the coil to the other. The field is similar to that produced by a short bar magnet and the coil acts as if it has a north pole on one face and a south pole on the other Right hand grip rule for determination of the direction of magnetic field produced by flow of current in a circular loop of wire or a coil. This rule states that, “Imagine your right hand is gripping the coil/ circular loop of wire in such a way that your fingers are curled in the direction of the conventional current flow, then the extended thumb points in the direction of North Pole”

Assessment 

The direction of the magnetic field around the straight current carrying conductor is reversed if the direction of flow of the current in the circuit is reversed.

The direction of the magnetic field around the

Ask the following questions from the students 1. What is the relation between the existence of the magnetic field around a current carrying wire and the flow of electric current in the circuit? (Expected answer: When a current is

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Teachers’ Guide

2.

3.

4.

5.

6.

7.

Lesson Plans: Physics

flowing through a current carrying conductor then a magnetic field exists around it. This magnetic field lasts as long as long as the current is flowing in the circuit). What is the effect on the direction of the magnetic field when the direction of the current in the wire is reversed? (Expected answer: The direction of the magnetic field is also reversed). What is the shape of the magnetic field around a straight current carrying conductor? (Expected answer: The magnetic field around a straight current carrying conductor is in the form of concentric circles with conductor at the centre). What is the name of the rule that is used to find out the direction of the magnetic field around straight current carrying conductor? (Expected answer: Right hand rule for determination of the direction of magnetic field around a straight current carrying conductor) When the current is passed through a circular loop of wire then what is the effect of the two faces of the loop? (Expected answer: The magnetic field pattern produced by a current flowing in a circular loop of wire shows that outside the coil, the field lines run in the loops from one face of the coil to the other. The field is similar to that produced by a short bar magnet and the coil acts as if it has a north pole on one face and a south pole on the other). What is the effect on the direction of the magnetic field when the direction of the current in the circular loop of wire is reversed? (Expected answer: The direction of the magnetic field is also reversed). When the current is passed through the coil of wire then where the strong magnetic field is produced? (Expected answer: When the

current is passed through the coil of wire then the strong magnetic field is produced along its axis that makes its one face south pole and the other face a north pole) 8. What is the name of the rule that is used to find out the direction of the magnetic field produced by the flow of current in a circular loop of wire or coil? (Expected answer: Right hand grip rule for determination of the direction of magnetic field produced by flow of current in a circular loop of wire or a coil) 9. Name some electrical instruments from your daily life that operate on the principles of electromagnetism.(Expected Answer : loud speaker , door bell , door latch , electric relay , magnetic circuit breaker etc)

Follow-up Project;  Make a poster through a library search or web search on the issue, “Role of electromagnets in developing a technology based modern world”

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Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 13

T O P I C

15

Turning effect on a current carrying coil in a magnetic field

Electromagnetism

Grade X

Direction of Force

Magnetic Field

Direction of Current

Students’ Learning Outcomes

Students will be able to:  describe that a force acts on a current carrying conductor placed in a magnetic field as long as the conductor is not parallel to the magnetic field. Information for Teachers 1. When a current is passed through a

conductor, a magnetic field is produced

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around it. When a current carrying conductor is placed in a magnetic field of a permanent magnet, a force F is produced. This force acts on the current carrying conductor and is at right angles to both the current direction I in the conductor and direction of magnetic field B. 2. The direction of the force can be found by the Flemings' Left Hand Rule that states, “If the thumb and the first two fingers of the left hand are held at right angles to one another, the thumb gives the direction of the thrust (force) if the first finger points in the same


Teachers’ Guide

Lesson Plans: Physics

direction as the field B and the second finger points in the same direction as the current I� 3. Magnitude of the force F on a current carrying conductor depends upon the strength of the magnetic field B, the magnitude of the current I, length L of the conductor and the orientation of the conductor in the magnetic field.

Material/Resources Required U shaped strong permanent magnet, bar magnets, Connecting wires, Battery cells, Compass needle, Power supply, Iron stand, Computer with internet connections to show PPt presentations and demonstrations.

Duration/Number of Period 120 mins/3 period Introduction Activity Ask the students to set up the apparatus using metallic c o n d u c t o r A B , b a t t e r y, connecting wires, switch etc according to the circuit diagram. Then the current is switched on in the circuit and the students are instructed to perform the following activities and make the observations to draw inferences.

No.

Activity performance

Observations

Inferences

1.

Set up the circuit as shown in the circuit diagram

Circuit is set up as per circuit diagram

Circuit is an open circuit

2.

Close the switch .Place a plotting compass under the conductor AB

The plotting compass shows a displacement

There is magnetic field produced due to the flow of current in the circui t in the conductor

3.

Now switch off the current in the circuit and again place a plotting compass under the conductor AB

The plotting compass does not show any displacement

There is no magnetic field when there is no current in the circuit

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Teachers’ Guide

Lesson Plans: Physics

Development Activity 1  Divide the students in groups to perform the experiment.  Tell the students to use the same experimental arrangement as in activity # 1 of the introduction and ask the students to perform the experiment step by step as instructed by him /her and record the observations on their observation sheet. Allow them to discuss the observations among themselves and guide them in drawing inferences from the observations. Experimental arrangement to observe the force on a straight current carrying conductor placed in a magnetic field. A: Orientation of the conductor - at right angles to the magnetic field direction 

No.

Activity performance

1. Now switch on the current in the circuit and bring a U shaped magnet closer to the conductor in such a way that:  its poles do not touch the conductor  These poles have conductor in between them in such a way such that it makes an angle of 90 degrees with the magnetic lines of force of the permanent magnet ( The length of the conductor AB is at right angles to the magnetic field produced by the magnet )

Observations

Inferences

As soon as the U shaped magnet is brought closer to the conductor as per instruction and precaution , there is a sudden displacement of the conductor A N

S B

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The displacement of the current carrying conductor when placed in the magnetic field of a permanent magnet shows that there is a force acting on the conductor


Teachers’ Guide 2. Reverse the direction of current in the circuit and bring a U shaped magnet closer to the conductor in such a way that :  its poles do not touch the conductor  These poles have conductor in between them in such a way such that it makes an angle of 90 degrees with the magnetic lines of force of the permanent magnet ( The length of the conductor AB is at right angles to the magnetic field produced by the magnet ) 3. Reverse the poles of the U shaped magnet and bring it closer to the conductor in such a way that :  its poles do not touch the conductor  These poles have conductor in between them in such a way such that it makes an angle of 90 degrees with the magnetic lines of force of the permanent magnet ( The length of the conductor AB is at right angles to the magnetic field produced by the magnet )

Lesson Plans: Physics As soon as the U shaped magnet is brought closer to the conductor as per instruction and precaution , there is a sudden displacement of the conductor but in the opposite direction to that as observed in step 4 A

N

The direction of force acting on the conductor is reversed when direction of flow of current is reversed in the conductor and the conductor is placed in a magnetic field of permanent magnet in such a way that it makes an angle of 90 degrees with the magnetic field direction

S B

As soon as the U shaped magnet is brought closer to the conductor as per instruction and precaution , there is a sudden displacement of the conductor but in the opposite direction to that as observed in step 5

The direction of force acting on the conductor is reversed when the direction of applied magnetic field is changed by reversing the poles of the magnet or by reversing the direction of the magnetic field

A S

N B

B:Orientation of the conductor - parallel to the magnetic field direction 4. Now reverse the poles As soon as the U When the conductor is magnets and bring the U shaped magnet is placed parallel to the shaped magnet closer to the brought closer to the magnetic field lines of force conductor in such a way that conductor as per of a permanent magnet , then no force acts on the  its poles do not touch the instruction and precaution , there is no conductor conductor displacement of the  These poles have conductor observed conductor in between them in a way that conductor is parallel to the

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Teachers’ Guide

Lesson Plans: Physics

magnetic lines of force of S N the permanent magnet ( A B The length of the b conductor AB is parallel to the magnetic field produced by the magnet ) 5. Invert the poles of the U As soon as the U When the conductor is shaped magnetic field and shaped magnet is placed parallel to the bring it closer to the brought closer to the magnetic lines of force , it conductor in such a way that conductor as per does not experience any force in any orientation  its poles do not touch the instruction and precaution , There is no conductor  These poles have conductor displacement observed in between them in a way that conductor is parallel to the magnetic lines of force S N A B of the permanent magnet ( The length of the conductor AB is parallel to the magnetic field produced by the magnet ) 6. Reverse the direction of the When the conductor is As soon as the U current in the conductor. placed parallel to the shaped magnet is Bring the U shaped magnetic lines of force, it brought closer to the permanent magnet and bring conductor as per does not experience any it closer to the conductor in force .Direction of flow of instruction and such a way that precaution , There is no the current in the displacement observed conductor and direction of  its poles do not touch the the magnetic field does not conductor affect this behavior. So we  These poles have conductor can infer that in between them in a way Whenever the straight that conductor is parallel to N current carrying conductor the magnetic lines of force A B is placed parallel to the of the permanent magnet ( S magnetic field – no force The length of the conductor acts on it AB is parallel to the magnetic field produced by the magnet ) C:Dependence of force on magnetic field strength B , length L of the conductor and current I in the conductor 7. Now use three permanent U The conductor is The force acting on the Shaped magnets of increasing deflected in a more conductor that produces strengths and repeat the step stronger way or to a displacement in the greater extent when 5 of the activity conductor is directly the permanent magnets proportional to the of greater strengths are magnetic field strength B of used the permanent magnet

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Teachers’ Guide 8. Increase the magnitude of current in the circuit and repeat step 5 of the activity

Lesson Plans: Physics The intensity of displacement again increases

9. Repeat the step 5 of the activity using conductors of different lengths

 When we increase the length of the conductor the intensity of the displacement is increased  When we decrease the length of the conductor , the intensity of the displacement is decreased 10. From the teachers’ Lab Flemings left hand rule manual/ text book , find out states, “If the thumb the statement of the and the first two fingers Fleming’s Left hand rule of the left hand are which describes the direction held at right angles to of the force acting on the one another, the thumb current carrying conductor gives the direction of placed in a magnetic field of a the thrust (force) if the permanent magnet first finger points in the same direction as the field B and the second finger points in the same direction as the current I” 11. Now come to the step 5 of When we extend our the activity and apply the left hand in such a way Fleming’s left hand rule to that first finger extend find the direction of the force in the direction of F that acts on the conductor magnetic field B and AB of length L carrying second finger points in current I When it is placed at the direction of the right angles to the field current flowing in the direction of a permanent conductor then force F magnet. of the conductor is along the Thumb .

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The force F acting on the conductor that produces displacement in the conductor is directly proportional to the magnitude of the current I flowing in the circuit The force F acting on the conductor is proportional to the length L of the conductor

The Flemings left hand rule can be used to find the direction of the force on a current carrying conductor placed in a magnetic field of a permanent magnet

The direction in which the force acts on a current carrying conductor is at right angles to both the magnetic field of a permanent magnet and the current flowing in the conductor. So


Teachers’ Guide

Lesson Plans: Physics

Direction of Force

Magnetic Field

Direction of Current

Activity 2 Demonstrate the following activity for the students to strengthen their concept. Proceed with the following statement : Let us find out the logical explanation for the force acting on a current carrying conductor when placed in the magnetic field of a permanent magnet at right angles to the magnetic field direction Step #1 Ask the students to use two pictures given below one showing the magnetic field of a permanent bar magnet on a paper and the other showing the magnetic field of a straight current carrying conductor carrying current towards the reader and out of the paper .The second picture is on the transparent sheet used in the over head projector. Pictures that can be used by the students

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Teachers’ Guide

Lesson Plans: Physics

x

A circle with a DOT shows that the current is coming OUT form the plane

A circle with a CROSS shows that the current is moving IN TO the plane

Field Pattern Of Straight Wire No. 1.

Questions What is the shape of the magnetic field of the permanent magnet?

2.

What is the shape of the magnetic field produced around a current carrying conductor (0)?

Expected answers The magnetic lines of force are straight lines originating from the north pole and terminating on the south pole The current in the conductor is flowing out of the paper towards the observer and the magnetic field is in the form of concentric circles with the conductor at the centre and is presented by (0) The direction of the magnetic field is anticlockwise.

Step#2 : Ask the students to put the paper on the table showing the magnetic field of a permanent bar magnet and ask them to put the transparent sheet having magnetic field due a straight current conductor traced on it in such a way that the magnetic field of the straight current carrying conductor is overlapping the magnetic field of permanent magnet drawn on the paper in the following way A Conductor in a Fixed Magnetic Field

N

F

A Current Carrying Conductor in a Fixed Magnetic Field

Force

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Teachers’ Guide

Lesson Plans: Physics

Step#3: Ask the students to observe carefully and answer the following questions: No. QUESTIONS 1. In what region the two fields that is one produced by the bar magnet and the other produced by the current carrying conductor are reinforcing each other? 2. In what region the two fields that is one produced by the bar magnet and the other produced by the current carrying conductor are cancelling the effect of each other? 3. Where is the region of resultant weaker magnetic field? 4. Where is the region of stronger magnetic field? 5. What should be the result of the existence of a weaker region of magnetic field and a region of stronger magnetic field in the same area? 6. What should be the direction of this force?

7. What should be the effect of this force?

8. What should be the direction of this force?

1. Can you predi ct the angles between direction of the magnetic field B, current I in the conductor and the resultant force F on the conductor? 2. Can you apply the Fleming’s left hand rule to confirm your answer?

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EXPECTED ANSWERS In the left hand region the two fields are reinforcing each other

In the right hand region

In the right hand region In the left hand region There should be a resultant force that should act on the conductor It should be directed from the region of stronger magnetic field to the region of weaker magnetic field The conductor should move from the region of stronger magnetic field to the region of weaker magnetic field. It should be at right angles to both the magnetic field direction of the permanent magnet and the current I flowing through the conductor. Yes three quantities that are field B, current I in the conductor and the resultant force F are perpendicular to each other. We can extend the left hand in such a way that first finger points in the direction of magnetic field produced by the bar magnet and the second finger points in the direction of flow of the current in the conductor then the thumb points in the direction of the force.


Teachers’ Guide

Lesson Plans: Physics

Conclusion/Sum up 

When a current is flowing through straight current carrying conductor , then a magnetic field is produced around it in the form of concentric circles with conductor at the centre

When the current carrying conductor is placed in the magnetic field of permanent magnet such that it makes an angle of 90 degrees with the magnetic lines of force of the permanent magnet then a force acts on the conductor and it is displaced.

Fleming's left hand can be used to find out direction of the displacement. The rule states that ,'If the thumb and the first two fingers of the left hand are held at right angles to one another, the thumb gives the direction of the thrust (force) if the first finger points in the same direction as the field B and the second finger points in the same direction as the current I”

There are four factors that are affecting the force acting on the current carrying conductor placed in the magnetic field of a permanent magnet. These are length L of the conductor, current I flowing in the conductor, Magnetic field strength of the permanent magnet and the orientation of the conductor in the magnetic field.

The direction of the force exerted on the current carrying conductor is at right angles to both the direction of flow of the current in the conductor and magnetic field direction Assessment

NO. 

QUESTIONS When a straight current carrying conductor is placed in a magnetic field of a permanent magnet then what happens? If we reverse the direction of fl ow of the current in the conductor then what happens? If we reverse the magnetic field direction of the permanent magnet by inverting it poles, then what happens? How we can increase the force acting on a current carrying conductor when placed in the magnetic field of a permanent magnet for its fixed orientation?

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EXPECTED ANSWERS It experiences a force and it gets displaced

It reverses the direction of the displacement of the conductor The direction of displacement reversed

is again

We can increase this force by increasing length or by increasing magnetic field strength of the permanent magnet or by increasing the current in the circuit


Teachers’ Guide

Lesson Plans: Physics

For what orientation in the magnetic field, the conductor experiences the maximum force?

For what orientation i n the magnetic field, the conductor experiences the minimum force?

Which rule is used to find out the direction of the force be ing exerted on a current carrying conductor placed in the magnetic field of a permanent magnet What is the statement of the Fleming’s left hand rule?

When the current carrying conductor is placed at right angles to the direction of the magnetic field , then it experiences the maximum force When the current carrying conductor is placed parallel to the direction of the magnetic field. , then it experiences no force Fleming’s left hand rule

If the thumb and the first two fingers of the left hand are held at right angles to one another, the thumb gives the direction of the thrust (force) if the first finger points in the same direction as the field B and the second finger points in the same direction as the current I”

Can you give a pictorial presentation of Fleming’s left hand rule?

Follow-up 

PICTURE DESCRIPTION Ask the students to describe the pictures in their own words as shown below in detail Magnetic Forces Acting on Parallel Current Carrying Conductors

Two parallel conductors carrying current in the same direction will attract each other

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Teachers’ Guide

Lesson Plans: Physics Magnetic Forces Acting on Parallel Current Carrying Conductors

Two parallel conductors carrying currents in opposite directions will repel each other, and they will set up a polarized magnetic field between themselves,.

Excursion The students can visit an electrical instruments workshop and observe the different electrical instruments using electromagnets as their key components. They are then asked to prepare short report on what did they observe there.

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Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 14

T O P I C

16

Analogue and digital electronic/logic gates

Introductory Electronics

Grade X

Students’ Learning Outcomes

    

Information for Teachers

Differentiate between analogue & digital electronics. State the basic operations of digital electronics. Identify and draw the symbols for the logic gates (OR, AND, NOT, NOR, NAND). State and verify the action of logic gates in truth table form. Demonstrate the simple uses of logic gates.

    

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Electronics circuit can be classified as digital or analogue. The number of states or voltages level is limited in a digital circuit, usually to two. An analogue circuit has an infinite number of voltage levels. T here are several kind of logic gates AND, OR, NAND, NOR. NOT gate functions as an inverter i.e. the output is always the opposite of the input.


Teachers’ Guide 

 

Lesson Plans: Physics

For the AND operation, the electronics circuit gives a HIGH output (1) only if all its inputs are HIGH. An OR gate is coincidence detector for L O W and conditions. NAND and NOR gates are the inverter of AND and OR gates respectively.

Figure 1 Pressure Gauge Syringe

Activity 2 Connect a switch S with a battery and a lamp (Figure 2). When the switch is open, the lamp is off. When the switch is closed, the lamp turns on. This systems has only two possible states.

Duration/Number of Periods 160 mins/4 period Material/Resources Required

syringe, pressure gauge, connecting tube, analogue and digital watch,

Switch open: Lamp off

 Switch closed: Lamp on Two state system is an example of a digital system. Some other digital quantities are. S

Introduction Digital Electronics has had a great impact on our society. It has given rise to calculators, digital watches, cell phone, micro computers and many other gadgets of daily uses. Many our homes and buildings have electronic control systems for cooling, heating and security. It is important to know the ways in which a small number of electronic components can be arranged to different ways to produce various kinds of control circuits. Most modern electronic systems are digital. Activity 1 Take a 50 mL syringe and connect it to a pressure gauge, as shown in Figure 1. Press the piston, the gauge shows pressure. More pressing of piston will show more pressure. The pressure on gauge can have any value from zero to a maximum value, depending on the push on the piston.

X=1

Figure 2

One of the States The other State

1

2

3

4

High

1

Yes

On

Low

0

No

Off

Example of analogue and digital systems and their wave form Analogue Watch

Analogue Signal

V t

This is an example of analogue system.

Figure 3

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Teachers’ Guide

Lesson Plans: Physics

Digital Watch

Switch: Switch is basic building block of all logic circuits. It is the combination of switches which provides us many different functions that digital electronics circuits can perform. Truth Label: A truth table is a good way to show the functions of a logic gate. It shows the output states of every possible combination of input states. The inverting circle: Some gates symbols have a circle on the output which means that their function includes inverting of the output. BASIC OPERATIONS AND LOGIC GATES: All information is converted into binary numbers using Boolean algebra based upon three basic operations 1. OR operation A*B 2. AND operation A+B 3. NOT operation A Logic Gates are the electronic circuit which in fact are combinations of electronic switches. They implement the various logic (Boolean) operations. They have two or more inputs except a NOT gate which has only one input. All gates have only one output. The letters A, B, C, are used to label inputs and 'x' is used to label output. Digital electronics are representations of Boolean Algebra, used in computers, cell phones and a number of consumer products. Digital circuits are usually made from large assemblies of logic gates. Remember that digital signals have only two values:“1” and “______” or

Digital Signal

V t Figure 4

Advantages of Digital Systems: Digital systems can only have certain definite values usually just on or off and hence are less affected by noise or distortions from other sources. A digital system is less affected by noise or distortions from other sources. Binary Code: Two states things are called Boolean variables represented by 0 and 1 known as binary numbers. Discussion points:  What is a code?  What code system can you name?  What are the advantages and disadvantages of a code system?  What are binary numbers? The on-off principle of the electric circuit is useful means of illustrating the binary numbers used in computer language. Binary means “two”. Numbers in binary are made up of only two digits 1 and 0. Each digit is a bit, which is short for “binary digits”. Computers process digital signals that are in the form of electric pulses. Each pulse stands for 1. Each missing pulse stands for zero. LINKS- MATHEMATICS: Explain base number system (e.g. 2 as the base of computer codes i.e. 20, 21, 22, 23.....).

“High Voltage” and “ ______ ________” or “On” and “_______” or “True” and “________”

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Teachers’ Guide

Lesson Plans: Physics

Development A=1

Activity 1 Construct the circuit diagram as shown in the figure (Fig.3) with the help of switches, wires, battery and bulb in parallel. Perform the activity and make the truth table for all combinations of inputs and outputs turn by turn for the four cases. Compare the truth table with that of an OR gate. Input A

Input B

OFF

OFF

OFF

ON

ON

OFF

ON

ON

OR Operations

B=1

OR GATE: OR gate can be regarded as two “switches” A and B connected in parallel. If either A and B or both switches are closed, the indicator lamp will light. The gate gives an output high (1) or when both inputs are high (1).

Output Bulb X

Truth Table for OR Gate Figure 5

A=0

B=0

X=1

X=0

A

B

Output

0

0

0

0

1

1

1

0

1

1

1

1

OR Gate A=1

Input A Input B

B=0 X=1

Figure 6

Activity 2

A=0

B=1

Output

Repeat the above activity connecting now in series combination as shown in Fig.8 and make the truth table for all combinations of inputs and outputs. Compare the truth table with that of AND gate.

X=1

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Teachers’ Guide

Lesson Plans: Physics

Input A

Input B

OFF

OFF

OFF

ON

ON

OFF

ON

ON

AND GATE AND gate can be regarded as two switches A & B connected in series. Output is high or one only when both inputs are high (1).

Output Bulb X

Truth Table for AND Gate

AND Operations

A

B

X= 0

A

B

Output

0

0

0

0

1

0

1

0

0

1

1

1

AND Gate

A=0

Input A

B=1

Output

Input B Figure 9

X=0 Activity 3

A=1

Switch in Opposite

B=0

X= 0

S

A=1

B=1 Figure 10 NOT GATE: Consider Figure 10, when switch S is open the lamp is on. But when the switch is closed the lamp is off due to short circuit. This is an example of NOT gate. The output of NOT gate is opposite to the input. It puts as an inverter. It has only one input.

X=1

Figure 8

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Teachers’ Guide

Lesson Plans: Physics NOR Gate

Truth Table for NOT Gate A

Output

A

0

1

B

1

0

A+B X = A+B Figure 13

NOT Gate (Inverter) Activity 4 Input

Output

A

A

CONTROL SYSTEMS USING LOGIC GATES Control systems are sensing circuits that monitor the conditions we want to control. They produce suitable digital signals either low or high voltages. The basic structure is shown in Figure 14.

Figure 11

NAND GATE It is a NOT gate coupled with AND gate.

Truth Table for NAND Gate

Input(s)

Process

Output(s)

B

A

X = A.B

0

0

1

Figure 14

0

1

1

1

0

1

1

1

0

The input section senses changes in some aspects of the environments, like temperature, smoke or light intensity. The output is some device that causes a change in the environment, like heater or a lamp. The process finds out what change in the inputs will cause the output to change. APPLICATIONS OF LOGIC GATES Logic Circuit: Burglar Alarm:

NAND Gate A

A.B

B

X = A.B

Figure 12

Consider a situation where by two switches A and B are placed, one each near the hinges of each door. When one door is opened, the switch is opened and burglar alarm starts sounding. So long the door remains closed, the switches are closed and burglar alarm remains off. The truth table for such a system to work is.

NOR gate It is a NOT gate coupled with OR gate.

Truth Table for NOR Gate B

A

X = A+B

0

0

1

0

1

0

1

0

0

1

1

0

This a truth table for NAND gate. Hence using a NAND gate, burglar alarm can be made.

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Lesson Plans: Physics

Truth Table Output X’

Input A

Input B

Input X

Closed

Closed

1

0

Closed

Open

0

1

Open

Closed

0

1

Open

Open

0

1

Logic Circuit: Burglar Alarm Connected to one Door

X

A

X’

Connected to other Door B

Alarm Figure 15

4.

Conclusion/Sum up

5.

 Basic logic gates are OR, AND and NOT.  OR and NOT combination makes NOR and the

combination of NOT and AND is called NAND gate.  The function of NOT gate is an inverter. “Output is always opposite of input.

6.

7. Assessment 1. The inputs of a gate are 1 and 0. Identify the gate if its output is (a) 0, (b) 1. 2. The output of two inputs of OR gate is 0 only when its: i. Both inputs are zero ii. Either input is zero iii. Both inputs are one iv. Either input is one 3. The output of AND gate is 1 only when its: i. Both inputs are zero ii. Either input is zero iii. Both inputs are one

8

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iv. Either input is one What is the name of the operation when single input = 0 gives an output = 1 When will the output of NAND gate be zero? The output of an NOT gate is connected to input of another NOT gate.  Draw up a truth table for their arrangement  Write a sentence to describe its effect If the input at A and B are at logic 1, give the correct output stage at 'x' for these gates. o AND gate o NAND gate o NOR gate What logic gate is represented by:

Input A

Input B

Output

0

0

1

1

0

1

0

1

1

1

1

0


Teachers’ Guide

Lesson Plans: Physics Follow-up

 

The bulb will light under certain conditions: What are they? The bulb will turn on when switches S1____________S2 or both are closed, for all other combinations the bulb is off. Switches in Parallel

S1

S2  The bulb will light under certain conditions:

What are they?  The bulb will turn on when switch S is ________, and turn off when switch S is______due to short circut.  This circuit is for illustration only! If this was a real circuit, what would happen to the battery, when switch S is closed?

Switch in Opposite

S

 State two advantages of transmission of

digital TV signal through optical fibers.

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Teachers’ Guide

Lesson Plans: Physics

UNIT

17

T O P I C

Components of ICT/ Communication technology

Information and Communication Technology

The students will: describe the components of information technology.

describe function and use of fax machine, cell phone, photo phone and computer.

identify various components of ICT.

make a list of the use of computer technology in various fields of daily life.

Grade X

Information for Teachers

Students’ Learning Outcomes

Lesson Plan 15

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The method of storing information, protecting information, processing the information, transmitting the information, and later retrieving information is called Information Technology.

Components of Information Technology:1. Hardware: 2. Software 3. Data 4. Procedures


Teachers’ Guide

Lesson Plans: Physics

5. People 

Information and Communications Technology (ICT) covers the computer hardware; the software programs; and the communications that occur between more than one different computerized devices.

ICT systems are those where the output from the system goes directly to a human being or into another ICT system.

Data is raw facts and figures or a set of values. Data has no meaning. Information is data that has been processed and put into context to give it meaning. Hardware consists of physical components of an ICT system e.g. Printer, scanner, monitor, server, switches. In many systems data is transmitted from one computer to another.

and let them observe the mode of working over there. 1

2

Software consists of Computer Programs that make the hardware do something useful. A series of actions or operations intended to achieve a result is called procedure. People consist those who are involved in testing of the system , sales, purchasing, finance, operations, internal and external personnel

3

4

Duration/Number of Periods 80 mins/2 Priod Material/Resources Required Computer, White board, commonly used hardware devices (printer, scanner, barcode reader, charts etc. 6

Introduction Activity 5

Take the students to the nearby super store

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Teachers’ Guide

Lesson Plans: Physics

Define the various pictures related to super store that may involve use of Information Technology

Picture Questions # 1. What the picture is representing? 2.

What the lines shown in picture depict?

Expected answers The picture is representing a super store where we normally go to buy various products of daily use. The lines show bar code. It’s a secret number shows different information about the product like Manufacturer #, Product # and Check digits etc. Bar Code Reader is the device used to scan the bar code information printed on any product.

3.

How information from bar code can be read?

4.

Have you seen bar code printed on any product?

Yes on many products like cola tin pack, packing of toothpaste and on the milk pack.

5.

How bill is generated?

6.

Have you noticed employee identification card of the salesperson? Does it have any useful information?

When sales person finished scanning bar codes from the products then eventually this information is printed on a paper by a small printer attached to the computer. Yes, identification card of the employee also contains bar code number.

Development Activity 1 

Describe the components of information technology. Take the students to the computer lab and brief them about the components of IT through a power point presentation. Let the students interact with the computers and then allow them to perform various tasks on the computer like exploring different softwares, windows properties, changing wallpapers and screen saver etc. Then offer the following questionnaire and ask them to fill it. Allow them to discuss the things with each other and provide full assistance and encourage their efforts.

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Teachers’ Guide

Observation

Lesson Plans: Physics

Activity What does it mean by hard ware?

Inferences All the devices that we can physically touch in the computer / IT lab called Hard ware

What do you mean by Soft wares?

Computer Programs that make the hardware do something useful.

What is digital technology? Use the internet to explore the definition of the Digital technology?

Digital describes electronic technology that generates, stores, and processes data in terms of two states: positive and non positive. Positive is expressed or represented by the number 1 and non-positive by the number 0.

What does it mean by data?

Raw facts that are used by programs

What people are doing here?

Being an important component of Information Technology, people are working with hardware, softwares, and process data to make it useful.

Ask the following questions 

Give definition of IT (“The method of storing information, protecting information, processing the information, transmitting the information, and later retrieving information is called Information Technology”).

List the Components of Information Technology:-

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Teachers’ Guide

Lesson Plans: Physics

(Hardware: The term hardware refers to machinery. This category includes the computer itself, which is often referred to as the central processing unit (CPU), and all of its support equipments. Among the support equipments are input and output devices, storage devices and communications devices. Software: The term software refers to computer programs and the manuals (if any) that support them. Computer programs are machine-readable instructions that direct the hardware parts (circuitry) of the system to function in ways that produce useful information from data. Programs are generally stored on some input / output medium, often a disk or tape. Data: Data are raw facts that are used by programs to produce useful information. Procedures: Procedures are the policies that control the operation of a computer system. People: Every system needs people if it is to be useful). Activity 2 Describe function and use of fax machine, cell phone, photo phone and computer. 

Prepare a charts containing pictures of Fax Machine, Cell Phone, Photo Phone and Computer

Show the chart to the students to make them understand how the mentioned devices work

Define purpose and advantages of each device

Tell the students that fax machine transfers data through telephone lines. It takes input in the form of paper or directly from the computer and produce output in printed form on paper and directly shows output in computer as a soft copy.

Tell the students that cell phones based on radio technology and it is a major source of communication.

Define the computer in understandable words that computer is an electronic machine which after analyzing and arranging the given information, presents it in a very time. It uses various hardware devices e.g. keyboard and mouse for input, printer and monitor for output purpose and

Also give some examples to explain the usage of computer e.g. in shopping malls, banks, ticket reservation centers etc.

Give advantages of computer use by telling them about fax machine, cell phone, photo phone and computer etc.

Fax Machine

Cell Phone

Photo Phone

100

Computer


Teachers’ Guide 

Lesson Plans: Physics

Ask the students to mention benefit of the device given below.

Device

Benefits 1. __________________________________ 2. __________________________________

3. __________________________________ 1. __________________________________ 2. __________________________________ 3. __________________________________ 1. __________________________________ 2. __________________________________ 3. __________________________________

Activity 3 Identify various Components of ICT 

Make the students vigilant to and tell them that today we are going to discuss very important topic Information and Communication Technology (ICT)

Give a brief definition of ICT as “Information and Communications Technology (ICT) covers the computer hardware; the software programs; and the communications that occur between more than one different computerized devices”

Define various components of ICT and quote most relevant daily life examples to make the students understand.

Activity 4 Assess the risks and benefits to society and the environment of introducing ICT (e.g. effects on personal privacy, criminal activities, health and transfer of information). 

After clearing the concepts of students about ICT its time to discuss benefits of ICT.

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Teachers’ Guide

Lesson Plans: Physics

How ICT is playing its positive role in our lives and how it made many tasks easier for us, let the students forward their comments on it.

After the comments of students discus the following topics to let the students know how and in which fields they can get benefit from ICT. E.g.

General benefits of ICT

Benefits for teachers

Benefits for students

Benefits for parents

Assign various topics to the groups of students and ask them to get information how we can get benefit from these.

Design an activity to see how much students know about various field where computer technology is used. Ask the students to connect the computer technology field with the relevant example Computer Technology Field

How it is working in our lives

Communication

Online shopping stores, marketing

Banking

Online job portals

Career Counseling

Discoveries regarding solar system

Science and Research

ATMs

Defense

Mobile phone technology, video conferencing, e-mail servers

E-commerce

Missile control technology

Assessment

Conclusion/Sum up 

Information Technology is use of science to enable  The flow  The storage, and  The handling of large amounts of information

1. What are the six components of an ICT system? (expected answer: Data, information, procedure, hard ware, software, people. 2. Define Hardware? (expected answer: Physical components of an ICT system e.g. Printer, scanner, monitor, server, switches.

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Teachers’ Guide

Lesson Plans: Physics Follow-up

Ask the students to browse the internet to investigate the Role of ICT in bridging the children of the world around for peace building efforts

Find out how IT has helped physically disable people such as the deaf and dumb to communicate with the world.

Draw a flow chart showing the procedure involved in purchasing a football from departmental store each student can prepare flow chart for the activity of his own interest.

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Teachers’ Guide

Lesson Plans: Physics

UNIT

Lesson Plan 16

T O P I C

18

Natural Radioactivity

Radioactivity

Grade X

Alpha Beta

Gamma

Information for Teachers

Students’ Learning Outcomes

Students will:  describe that the three types of the radiation are alpha (), beta () and gamma( )rays  state for radioactive emissions: 1. their nature 2. their relative ionizing effects 3. their relative penetrating abilities  explain that an element may change into another element when radioactivity occurs  represent changes in the composition of the nucleus by symbolic equations when alpha or beta particles are emitted

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Some materials naturally emit ionizing radiation which can be penetrating and highly dangerous. Such materials are said to be radioactive and their radiation can be of three types. o Alpha radiation o Beta radiation o Gamma radiation The phenomenon of spontaneous emission of radiation from some elements like radium and uranium is called natural radioactivity. The radiation emitted by the radioactive


Teachers’ Guide

Lesson Plans: Physics

substances consists of three types. Alpha rays, beta rays and gamma rays. The direction of deflection of alpha rays in the magnetic field indicates that these are positively charged particles. The direction of deflection of beta particles in the magnetic field indicates that these are negatively charged particles. The direction of deflection of Gamma ray Photons in the magnetic field show that these radiations consist of photons only. Duration/Number of Period

40 mins/1 period Material/Resources Required board, chalk/marker, pictures and textbook etc.

Negative ion

Introduction Activity 1 Draw the following diagrams on the black board and explain it to the students. Students copy these pictures on their note books. Neutral atoms

Positive ion 

105

Ions are nothing more than atoms or molecules that have gained or lost an electron. Those that have lost an electron are called positive ions, while those that have gained an electron are negative ions. Ions are formed when an electron is detached from a neutral molecule (or atom). The molecule losing an electron becomes a positive ion and the molecule gaining an electron becomes a


Teachers’ Guide negative ion.  If the electrons are detached from molecules in a gas, ions are produced and gas is said to be ionized  The molecules with electrons missing are the positive ions  Detached electrons join to other molecules to form negative ions.  As ions in a gas are free to move so an ionized gas can conduct. Now tell the students when atoms change into positive and negative ions is called ionization. Activity 2 Explain the concept of radioactivity by consulting periodic table with students.

Lesson Plans: Physics

Development Guide the students about the nature of Alpha, beta and gamma radiation. Briefs the students about the radioactive elements in the following way and writes important points on the board.  Henry Becquerel discovered in 1896 that certain elements whose atomic numbers are greater than 83 (z>83) are unstable.  These elements disintegrate to emit three kinds of radiation called alpha, beta and gamma radiation such elements are called radioactive elements.  The process of emitting radiation is called radio activity. The radioactive elements are Radium (Z=88), Uranium (Z=92) and Polonium (Z=84). Since it is a natural phenomenon therefore the process is called natural radio activity and the elements are called natural radioactive elements. Activity 1 Draw the following picture on the board.

Photographic plate

Lead block

Now enlist the elements having atomic 84 85 86) number greater than 82. (83 Bi Po At Rn etc.

Source

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Teachers’ Guide

Lesson Plans: Physics

 

Gamma ray = ultra-high-energy non-visible light (no electric charge)

Alpha particle = helium nucleus (+2 electric charge)



Magnet

Beta particle = electron ( - 1 electric charge) Lead block

Radium sample

Then explain the picture to the students and then asks the following questions from students: 1. Where the radioactive source is placed? (Expected answer: The radioactive source is placed in the lead chamber). 2. What is the mode of emission of the radiation from source and while travelling inside of the chamber? (Expected answer: The radiation shoots out from the radioactive source and move in a straight line before entering in the vacuum chamber). 3. What has been applied in the vacuum chamber? (Expected answer: Magnetic field is applied in the vacuum chamber perpendicular to beam of radiation entering in the chamber and is directed into the paper). 4. What happens in the ionization chamber? (Expected answer: The radiation splits up into three parts) 5. What important result you can draw by the beam of radiation deflected towards left? (Expected answer: If we use the Flemings left hand rule to the situation when the wire is carrying current at right angles to the direction of the magnetic field (into the paper) then a force is exerted on the current carrying conductor at right angles to both B and I The direction of the deflection shows that the beam that is deflected towards left consists of particles having positive charge. 6. What is the name of the radiation deflected towards left? (Expected answer: The radiation that deflects towards left consists of particles bearing positive charge and this type of radiation is called alpha rays). 7. What is the name of radiation that is deflected towards right? (Expected answer: The radiation

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Teachers’ Guide

Lesson Plans: Physics

that deflects towards right consists of particles bearing negative charge and this type of radiation is called beta rays). 8. What is the name of radiation that passes without suffering any deflection in the vacuum chamber and forms a spot on photographic plate? (Expected answer: The radiation that is neither deflected towards right nor towards left but travels in a straight line under the applied magnetic field in the vacuum chamber is called Gamma Ray radiation). Explain that nature of the natural radio activity can be studied by applying the electric field even in the following way: Lead block

Aligning slot

Electric field

Radioactive source   

Detecting screen

Alpha particles (positive charge)

gamma rays (no charge)

particles  Beta (negative charge)

Alpha particles move toward the negative plate. Beta particles move toward the positive plate. Gamma rays are not deflected

Activity 2 Draw the following diagram on board and tell students about the concept of penetrating power of radioactive rays.

Lead block

Paper

Wood

  

 

Lead

Radioactive source (Comparison of penetration powers of the alpha, beta and gamma rays)

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Some gamma rays


Teachers’ Guide

Lesson Plans: Physics

Activity 3

5. When Uranium 238 emits an alpha

Draws the following picture on the black board and ask the students to copy it on their note books then explain the following figures to them. Emission of Alpha Particles in a nuclear decay reaction. The radioisotope Uranium-238 emits alpha radiation and is transformed into another radioisotope, Thorium-234.

particle what is then change in its atomic number? (Expected answer: Its atomic number decreases by 2 and the atomic number of the product becomes 90). 6. What is name of the element in the periodic table that has an atomic number Z=90? (Expected answer: The name of the element having Z=90 is Thorium 234). 7. What is the change in the mass number A of the Uranium when it emits an alpha particle? (Expected answer: The mass number decreases by 4). 8. Which one is the parent element in the above mentioned nuclear decay reaction? (Expected answer: Uranium 238). 9. Which one is the daughter element in the above mentioned nuclear decay reaction? (Expected answer: Thorium 234). Emission of beta rays Carbon-14 emits a beta particle as it decays and forms nitrogen-14.

4 He 2 Alpha particle 234 Th 90 238 U 92

When an atom loses an alpha particle, the atomic number of the product is lowered by two and its mass number is lowered by four

1. What is the atomic number of Uranium?

(Expected answer: The atomic number Z of Uranium is 92). 2. What is the mass number A of Uranium? (Expected answer: The mass number A of Uranium is 235). 3. What is the mass number A of ra d i o i s o t o p e o f U ra n i u m - 2 3 8 ? (Expected answer: The mass number A of the radioisotope of Uranium is 238). 4. How many protons and neutrons would be lost by Uranium 238 if it wants to emit an alpha particle? (Expected answer: It would have to get rid of a particle having two protons and two neutrons to emit an alpha particle)

The nitrogen-14 atom has the same mass number as carbon-14, but its atomic number has increased by 1. It contains an additional proton and one fewer neutron. 1. What is the atomic number of Carbon? (Expected answer: The atomic number Z of Carbon is 6). 2. What is the mass number A of radioisotope of Carbon-14? (Expected

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Teachers’ Guide

Lesson Plans: Physics 0e -1

above mentioned nuclear decay reaction? (Expected answer: Carbon14). 8. Which one is the daughter element in the above mentioned nuclear decay reaction? (Expected answer: Nitrogen 14). Gamma rays emission

14 C 6 14 N 7

3.

4.

5.

6.

7.

A high-energy photon emitted by a radioisotope is called a gamma ray. The high-energy photons are a form of electromagnetic radiation. Nuclei often emit gamma rays along with alpha or beta particles during radioactive decay 

answer: The mass number A of the radioisotope of Carbon is 14). What is the effect on the composition of the Carbon -14 nucleus if beta particle is emitted from the nucleus? (Expected answer: When one neutron in the Carbon-14 nucleus is converted into proton then an electron is created and this electron shoots out from the nucleus as soon as it is formed. The mass number of remains the same but there is a change in the atomic number. The Z for the product is one time greater that of the nucleus under decays). When Carbon -14 emits a beta particle what is then change in its atomic number? (Expected answer: Its atomic number increases by 1 and it becomes 7). What is name of the element in the periodic table that has an atomic number Z=7? (Expected answer: The name of the element having Z=7 is Nitrogen -14) What is the change in the mass number A of the Carbon -12 when it emits a beta particle? (Expected answer: The mass number remains the same). Which one is the parent element in the

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In the first nuclear decay reaction ,Thorium -90 is converted into Radium 88 by emitting an alpha particle , what additional emission you can notice in the reaction equation ? (Expected answer: When the nucleus of Thorium90 emits an alpha particle, then it is changed into Radium -88 and the nucleus Radium -88 is left in the excited state –high energy state. in order to get stability, it emits a high energy photon called gamma ray). In the second nuclear decay reaction, Thorium -90 is converted into Protactinium 91 by emitting a beta particle, what additional emission you can notice in the reaction equation? (Expected answer: When the nucleus of Thorium-90 emits a beta particle, then it is changed into Protactinium -91 and the nucleus Protactinium -91 is left in


Teachers’ Guide

Lesson Plans: Physics

the excited state –high energy state. In order to get stability, it emits a high energy photon called gamma ray). Is there any change in the atomic number Z when there is a gamma emission? (Expected answer: There is no change in the number Z during a gamma ray emission) What is the nature of the gamma rays? (Expected answer: Gamma rays are high energy photons How the gamma ray photon is different from X-rays? (Expected answer: The gamma ray photon is emitted from the nucleus when the nucleus switches from its excited state to its ground state X-rays are emitted when the atom is in the excited state due to shifting of the inner most shell electrons to the outer most shells and jumping back of electrons to the inner most shells.

Assessment

Conclusion/Sum up 

positively charged particles The direction of deflection of beta particles in the magnetic field indicate that these are negatively charged particles The direction of deflection of Gamma ray Photons in the magnetic field show that these radiations consist of photons only.

Some materials naturally emit ionizing radiation which can be penetrating and highly dangerous. Such materials are said to be radioactive and their radiation can be of three types  Alpha radiation  Beta radiation  Gamma radiation The phenomenon of spontaneous emission of radiation from some elements like radium and uranium is called natural radioactivity The radiation emitted by the radioactive substances consists of three types. Alpha rays, beta rays and gamma rays The direction of deflection of alpha rays in the magnetic field indicate that these are

1. An  particle contains: a. Two neutrons b. Two protons c. Two neutrons and two protons. d. Two electrons 2. Which material is best for making a box for the safe storage of a radioactive substance? a. aluminum b. glass c. graphite d. lead 3. Which of the following has the same properties as a beta particle? a. a helium nucleus b. an electron c. a neutron d. a proton 4. Which of the following pair of particles/ atoms /radiation is deflected by both electric and magnetic fields? a. Alpha particle and gamma radiation b. Beta particle and gamma radiation c. Alpha particle and a hydrogen atom d. Alpha particle and beta particle Answer Key: 1. c 2. a 3. b 4. d

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Teachers’ Guide

Lesson Plans: Physics Follow-up

 

Investigate the hazardous effects of radiations on human beings who work inside the zones of radioactivity. Ask the students to prepare a summary of the Radioactive Decay Processes.

Summary of the Radioactive Decay Processes Type of the Particle Emitted Change in Mass Number Change in Atomic radioactive decay of the parent element Number of parent element Alpha Decay Beta Decay Gamma Emission Expected Answer:

Summary of the Radioactive Decay Processes Type of the Particle Emitted Change in Mass Number Change in Atomic radioactive decay of the parent element Number of parent element Alpha Decay Helium Nuclei Decreases by 4 Decreases by 2 Beta Decay Beta Particle No change Increases by 1 Gamma Emission Photon No Change No Change  Which type of radiation is a form of electromagnetic radiation?  which travels fastest alpha, beta or gamma radiation?  Why are gamma rays unaffected in a magnetic field?

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Teachers’ Guide

Lesson Plans: Physics

Glossary Alternating current Ammeter Analogue electronics Centre of Gravity Computer Diffraction Digital electronics Direct current Dynamics Effort Effort arm Effort Moment Electric current Electric field Electric power Electromagnetic field Electromagnetic force Electromagnetic waves Electromotive force

A current whose direction changes continuously An instrument used to measure the current in a circuit Name of processing quantities of continuous increase decrease or remaining constant The point of body where its weight acts A machine which can communicate and analyze information efficiently and has a vast and long last memory Bending of waves round an obstacle Name of processing data provided in the form of digits Current which always flows in one direction Study of motion of bodies under action of forces Force applied on the machine The intermediate distance between fulcrum and effort Product of effort and effort arm The rate of flow of electric change through any cross sectional area. That space round a charged body in which another charge experiences its effect in the form of a force Amount of energy obtained from electric current in unit time Production of magnetic field due to passage of electric current through a conductor The phenomena in which e.m.f is produced due to relative motion of coil and magnet Such waves, which do not require material medium of their propagation

Equilibrium Floppy Force Friction

The energy needed to move one coulomb charge through the whole circuit including the battery Electronics is the study and use of circuitry involving components such as resistors, diodes, transistors, capacitors, inductors and integrated circuits. We divide the electronics into two main branches: one is analogue and the other is digital. A body whose acceleration is zero A device used for storing computer data The agent that changes or tends to change the state of a body The force of resistance against the relative motion between two surfaces

Fulcrum

The point around which lever revolves

Electronics

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Teachers’ Guide Fuse Galvanometer Information technology Joule Kilowatt hour Kinematics Laser disc or CD Lever Load Load arm Load moment Mechanics Power

Pressure Rolling Friction Short-circuit Significant Figures Sliding Friction Speed Speed Stable Equilibrium Static Friction Work

Lesson Plans: Physics A special wire that protects an electric circuit. If the current gets too large, the fuse melts and stops the current. An instrument which indicates the current in a circuit Scientific method of collecting and arranging information and import them to others The unit of work in system international Quantity of that energy which is obtained from one kilowatt power in one hour Study of motion of bodies without taking into consideration the mass and force A device used to store data with the help of digital technology A strong bar revolving around some point is equal to 9.46x10 15m Resistance or lifted up weight The intermediate distance between fulcrum and load Product of load and effort arm The branch of Physics which deals with the study of motion of bodies is known as Mechanics Amount of energy transferred every second. The energy can be transferred from somewhere (e.g. a power station) or to somewhere (e.g. an electric kettle.) Power = energy transferred / ti me taken. The effect of a force spread out over an area. Pressure = force / area. The friction produced during the motion of one body over the other with the help of whets Unwanted branch of an electrical circuit that bypasses other parts of the circuit and causes a large current to flow. In a measurement, the correctly known digits and the first doubtful digit The friction between two surfaces sliding against each other Distance covered by a body in certain time How far something moves every second. Average speed = distance travelled / time taken. The condition of a body in which it comes to its original condition after being disturbed The force of friction arising due to applied external force before motion Energy transferred when a job is done. Work = force x distance moved in direction of force.

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Phy9 10  

A digital book for 9th & 10th Physics. With all audio & video lectures. نہم اور دہم فزکس کے لیے مکمل کتاب۔

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