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Topic: How do you light bulb? Introduction Electricity is used as energy in our lives variously. To light the bulb is one way to use electricity. This topic, we are

Example

going to learn how to light a bulb with a dry cell.

Subub-topic1: opic1: Light Light with a bulb bulb and a dry cell. Question 1 How do you light a bulb?

Experiment 1 Identify in which connection a bulb lights.

MATERIALS Dry cell

Bulb Socket

- (Negative) terminal

+ (Positive) (Positive) terminal

Cord 1.

Try a variety of connection with the bulb and dry cell. And identify in which connection a bulb lights. Then, sketch them and write results Example

1


2. Organise results

3. Discussion :Make a conclusion from result About : How do you connect, connect, if you want a bulb to light?

Conclusion 1 If you want a bulb to light, + (positive) and – (negative) must be connected with cords. cords

Electric circuit and Electric current When + (positive) and – (negative) are connected with cords, cords become a path like as a ring which electricity can pass. This path is called “Electric Electric circuit”. circuit If there is a bulb in the electric circuit, Electricity pass through the bulb and the bulb lights. Electricity flow from positive to negative. This flow is called “Electric current” current”.

Example of circuit A circuit shown below is a twisted ring. Even in this circuit a bulb can light. As long as + and – terminals are connected with cord and bulb, bulb lights. Because, electric current pass through a bulb. +

-

Exercise: Answer light or not for each of the following circuit. a)

b)

Trace from + to – to identify + and – terminals are connected with cord and bulb. 2

c)


Question 2 .If circuit is cut down, what will be happen?

Experiment2 Cut a circuit MATERIALS Bulb

Dry cell

Socket +

-

Cord

1. Cut a cord nearby negative terminal. Result: Result: Light die

2. Cut a cord nearby positive terminal Result: Result: Li Light die

Conclusion onclusion 2 Wherever in the circuit you cut, light would die.

3


Disconnected circuit Electric current is like as flow of cars going around a circular road. Right diagram show electric current flow circuit smoothly.

When the road breaks down, all the cars will stop at the same time. Same as this, when the cord (wire) is disconnected, electricity don’t flow. That’s why a bulb doesn’t light

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Question 3 Which part of bulb do you connect with cord or dry cell, If you want it to light? light?

Experiment3 Experiment3 Light a bulb without socket. MATERIALS Bulb

Pair of cords

Dry cell +

Sticky tape

15~20 cm

How to prepare cords and remove vinyl of cord 1. Cut only vinyl

2. Remove vinyl

3. Twist wire

4. Do the same things at both side

1 .Try a bulb to light with one and two cords Example

You can use sticky tape

Adbice: Don’t connect like shown as below (short circuit) bice: Don’ Don’ Don’t connect ONLY CORD with dry cell. cell. And don’ don’t attach wire to wire. Circuit will heats up.

5


2. Organise result

3.Discussion : make a conclusion About: About: Which part of bulb did you connect with cord or dry cell, cell, when bulb lighted ?

Conclusion onclusion 3 When each terminal (positive and negative) is connected to side and bottom respectively, a bulb is light

side side bottom Side

Bottom

Question from conclusion 3 How is inside of bulb? How is the path from bottom to side?

6

bottom


Inside of bulb The inside of bulb is shown left. When the bulb is connected in circuit, electric current pass through Filament and it emits light. Filament Socket

Exercise Answer light or not for each of the following circuit. If you can’t predict, you can make circuits and identify. a)

e)

b)

c)

f)

g)

Challenging exercise Bulbs shown below don’t light. Explain why each bulb doesn’t light. a)

b)

7

d)

h)


Sub-topic2:

Conductor and Insulator

Question 1 What kind of materials can link disconnected chords?

Experiment 1 Find materials which can light light a disconnected circuit. MATERIALS

Various Disconnected circuit

1. Touch things with disconnected cords. And then, write down table shown as below

Example thing

8

result


2. Organise results

Spoon (iron)

Scissors (iron)

Coin

Ruler (plastic)

Aluminium foil

Ruler (plastic)

Board (wood)

Ruler (plastic)

Bag (plastic)

Scissors (plastic)

3. Discussion: make conclusion from result About: How is the difference between things which can link disconnected chord and things things which can’ can’t link it? (If things link a disconnected circuit, a bulb in circuit would light. ) Conclusion The feature of things which can link a disconnected circuit is metal. (Iron, aluminium, copper, etc)

Conductor and insulator

Conductor

When the metal link cords as a diagram shown left, electricity pass through it. Substances that allow electricity to pass along it or through it are called conductor So, the metal is the conductor. While things which can’t link a disconnected circuit are made of plastic, wood or paper. These substances don’t allow electricity pass through it. These are called insulator 9


Exercise 1. Which is rubber band conductor or insulator? 2. Answer light or not for each of the following circuit.

a)

c)

b) Wood

d)

d) Challenging

Challenging exercise Connections shown as below aren’t light. Explain why they aren’t light

a)

b)

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1. Electric Circuit

If positive terminal and negative terminal

If positive terminal and negative terminal are

are not connected, it’s not light.

connected, it’s light. This connection is called

And even, if circuit is breaking down, it’s

electric circuit. circuit.

not light

2. Conductor and insulator Stop electricity

If you link disconnected line by conductor, conductor

If you link disconnected line by conductor, conductor

electricity pass through it and a bulb light.

electricity pass through it and a bulb light.

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Handicraft Make switch 2. Wrap two piece of card board

1. Cut a cardboard following diagram

in aluminium foil

2cm

shown as below

2cm

6cm

4. Cut a corrugated card box and staple

3. Bend a long piece of cardboard

cord, two pieces and a piece of card box.

4cm 6cm

Switch

Turn off

Turn on

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