Electricity and Magnetism 9.3.5 Practice_ Points Possible: 25.

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9.3.5 Practice: Electricity and Magnetism Physics Points Possible:25

Practice Name:

Carson Limbaugh

Date: Question 1 (4 points) a. Make a drawing of the electric field lines around a positive charge, then make a second drawing of the electric field lines around a negative charge. (1 point)

Positiv e

Negative

b. What is the mathematical equation for the electric force between two charges? Identify each variable. (1 point) F=k times q1q2/r squared c. Describe the direction of the electric force between two opposite charges, between two like charges, and when a charge is in an electric field. (1 point) They attract each other and same like charges repel. d. A metal sphere is neutral because it has an equal number of protons and electrons. Draw how the charges in the sphere are redistributed when a negatively charged rod is brought near it. (1 point)

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Question 2 (3 points) a. Describe how electric potential energy, kinetic energy, and work change when two charges of opposite sign are placed near each other. (1 point) Kinetic energy, potential energy and work all increase b. Complete the table to show the effect of each change on each electric quantity. (1 point) Change

Effect on electric force

Effect on electric potential energy

Effect on potential difference

Multiply one charge by 2

increase

decrease

increase

Multiply distance by 2

decrease

increase

decrease

c. What is the mathematical equation for capacitance? Identify each variable. (1 point) C = εA/d

Question 3 (4 points) a. What is the mathematical equation for Ohm’s law? Identify each variable. (1 point) V=IR

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b. What is the potential difference across a 15 Ω resistor that has a current of 3.0 A? (1 point) 45v

c. Review quantities associated with electric circuits by completing the table. (1 point) Symbol

Units (full name and abbreviation)

Potential difference

V

Joules per coulomb

Current

l

Voltage/resistance

Resistance

R

Voltage/Current

Capacitance

F

Farad

Charge

q

d. Fill in the blanks in the following paragraph to correctly identify the conductive properties of materials. (1 point) A metal such as copper is a(n) conductor because it provides a pathway for electric charges to move easily. A material such as rubber is a(n) insulator because it stops the flow of electric charges. A material that partially conducts electric current is a(n) semiconductor. These materials include silicon elements.

Question 4 (3 points) a. Review the properties of meters used in electric circuits by placing an X in the correct column.

(1 point) Ammeter Measures current

Voltmeter

x

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Measures potential difference

x

Connected in parallel

x

Connected in series

x

Measurement expressed in amperes

x

Measurement expressed in volts

x

Measures the amount of charge per second passing through

x

Measures the change in energy per unit charge between two points

x

b. Write a few sentences comparing three different kinds of circuits: complete, open, and short circuits.

A complete circuit is where a full circuit is fully closed. An open circuit does not close the circuit.

A short circuit has no resistance

c. Describe how fuses and circuit breakers protect against electrocution and household fires.

How do you restore a broken circuit after the problem has been corrected? (1 point)

The fuse breaks the circuit if the current gets dangerously high.

Question 5 (4 points)

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a. Examine the lightbulbs in the circuit below. Write a sentence explaining what would happen if lightbulb A burned out. Repeat this for lightbulbs B, C, and D. (1 point)

If a got turned off then this would break the circuit

b. What is the equivalent resistance if you connect three 10.0 Ω resistors in series? (1 point)

30

c. What is the equivalent resistance if you connect three 10.0 Ω resistors in parallel? (1 point)

3.21

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d. Calculate the current in each 10.0 Ω resistor in the series circuit and in the parallel circuit if the power supply is 60.0 V. (1 point) 187

Question 6 (3 points) a. What are the ends of a magnet called? Describe the forces that occur when two magnets are brought close together. (1 point) North and south poles. Magnetism happens when they brought together.

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b. Draw a bar magnet, label its poles, and draw the magnetic field lines around it. (1 point)

N

S

c. Explain what happens when you cut a magnet in half. (1 point) The poles will always be on both sides of the magnet

Question 7 (4 points) a. Compare permanent magnetism, induced magnetism, and electromagnetism. (1 point) Permanent magnets are materials where the magnetic field is generated by the internal structure of the material itself. Magnetism is a force of nature produced by moving electric

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charges.Electromagnetism is defined as an attraction between particles which is defined as created by electricity

b. Fill in the blanks in the following paragraph to correctly identify the properties of devices that use electromagnetism. (1 point) A(n) generator changes mechanical energy into electricity. A(n) motor changes electrical energy into mechanical. A(n) transformer changes the voltage of an alternating current. A(n) step-down transformer has more loops in the primary coil than in the secondary coil. A(n) step-up transformer has fewer loops in the primary coil than in the secondary coil. c. Describe how to use right-hand rules to relate the directions of magnetic fields, currents, moving charges, and forces. (1 point) Determine the direction of the magnetic force on a positive moving charge.Point your right thumb in the direction of the velocity, your index finger in the direction of the magnetic field, and your middle finger will point in the direction of the resulting magnetic force. Negative charges will be affected by a force in the opposite direction

d. What is the mathematical equation for calculating the force on a charged particle moving through a magnetic field? Identify each variable. (1 point) F = qE + qv × B. E is electric field B is magnetic field

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