Download Electromagnetism Worksheets

Electromagnetism Worksheets
Jean Brainard, Ph.D.
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Printed: December 5, 2013
AUTHOR
Jean Brainard, Ph.D.
EDITOR
Bradley Hughes, Ph.D.
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Chapter 1. Electromagnetism Worksheets
C HAPTER
1
Electromagnetism
Worksheets
C HAPTER O UTLINE
1.1
Electricity and Magnetism
1.2
Using Electromagnetism
1.3
Generating and Using Electricity
1
1.1. Electricity and Magnetism
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1.1 Electricity and Magnetism
Lesson 25.1: True or False
Name___________________ Class______________ Date__________
Determine if the following statements are true or false.
_____ 1. Oersted’s discovery of the connection between electric currents and magnetic fields was a lucky accident.
_____ 2. Oersted discovered electromagnetism when he placed a compass near a battery.
_____ 3. The direction of the magnetic field around a wire is parallel to the direction of the current through the wire.
_____ 4. The magnetic field around a wire is stronger when more current is flowing through the wire.
_____ 5. The magnetic field Oersted created around a wire was too weak to affect a nearby compass.
_____ 6. A compass always points to Earth’s north magnetic pole even when placed near a magnet.
_____ 7. The right hand rule states that you should always hold a compass in your right hand.
Lesson 25.1: Critical Reading
Name___________________ Class______________ Date__________
Read this passage from the text and answer the questions that follow.
Electric Currents and Magnetic Fields
The magnetic field created by a current flowing through a wire surrounds the wire in concentric circles. The magnetic
field is stronger if more current is flowing through the wire. The direction of the magnetic field depends on the
direction that the current is flowing through the wire. A simple rule, called the right hand rule, makes it easy to
find the direction of the magnetic field if the direction of the current is known. When the thumb of the right hand is
pointing in the same direction as the current, the fingers of the right hand curl around the wire in the direction of the
magnetic field.
Questions
1. Describe the magnetic field around a wire that is carrying current.
2. Explain how to find the direction of the magnetic field around a wire if the direction of the current is known.
Lesson 25.1: Multiple Choice
Name___________________ Class______________ Date__________
Circle the letter of the correct choice.
1. Oersted discovered that electric currents generate magnetic fields in
2
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a.
b.
c.
d.
Chapter 1. Electromagnetism Worksheets
1600.
1820.
1980.
2000.
2. When Oersted made the discovery in question 1, he was trying to demonstrate that
a.
b.
c.
d.
electricity and magnetism are not related.
electric currents create magnetic fields.
compasses can detect magnetic fields.
magnetic fields create electric currents.
3. The magnetic field created by current flowing through a wire
a.
b.
c.
d.
surrounds the wire in concentric circles.
is just like the magnetic field of a bar magnet.
has the same direction as the current.
has the opposite direction to the current.
4. According to the right hand rule, the fingers of the right hand curl around the wire in the same direction as the
a.
b.
c.
d.
current.
compass.
conductor.
magnetic field.
5. Factors that affect the magnetic field around a wire that is carrying current include
a.
b.
c.
d.
amount of current.
direction of current.
position of compass.
two of the above
Lesson 25.1: Matching
Name___________________ Class______________ Date________
Match each definition with the correct term.
Definitions
_____ 1. material through which electric current can flow
_____ 2. continuous flow of electric charges
_____ 3. device that points toward a north magnetic pole
_____ 4. way to find the direction of the magnetic field around a wire carrying electric current
_____ 5. magnetism produced by electric current
Terms
a. electromagnetism
b. compass
c. right hand rule
d. electric current
e. electric conductor
3
1.1. Electricity and Magnetism
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Lesson 25.1: Fill in the Blank
Name___________________ Class______________ Date________
Fill in the blank with the appropriate term.
1.
2.
3.
4.
The scientist who discovered how electricity and magnetism are related was __________.
The direction of the magnetic field around a wire depends on the direction of the __________.
A crane magnet is a type of magnet called a(n) __________.
Oersted investigated the magnetic field around a wire by placing a(n) __________ at different locations around
the wire.
5. To apply the right hand rule, your thumb should point in the same direction as the __________.
Lesson 25.1: Critical Writing
Name___________________ Class______________ Date________
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.
Explain how you could use a wire and a battery to create a magnetic field.
4
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Chapter 1. Electromagnetism Worksheets
1.2 Using Electromagnetism
Lesson 25.2: True or False
Name___________________ Class______________ Date__________
Determine if the following statements are true or false.
_____ 1. The magnetic field of a solenoid has north and south poles.
_____ 2. An electric motor contains two electromagnets.
_____ 3. An electromagnet contains a solenoid.
_____ 4. A solenoid has a magnetic field only when current flows through it.
_____ 5. Very few devices contain electromagnetics.
_____ 6. The clapper of an electric doorbell is an electromagnet.
_____ 7. When the clapper of a doorbell strikes the bell, it opens an electric circuit.
_____ 8. The electromagnet of an electric motor is connected to a permanent magnet.
_____ 9. Only the shaft of an electric motor turns when current flows through the motor.
_____ 10. The poles of the electromagnet in an electric motor keep reversing.
Lesson 25.2: Critical Reading
Name___________________ Class______________ Date__________
Read this passage from the text and answer the questions that follow.
Electromagnets
An electromagnet consists of a solenoid (soil of wire) wrapped around a bar of iron or other ferromagnetic material.
When current flows through the solenoid, it gives it a magnetic field like a bar magnet. The magnetic field of the
solenoid magnetizes the ferromagnetic bar by aligning its magnetic domains. The combined magnetic force of the
magnetized iron bar and the wire coil makes an electromagnet very strong. In fact, electromagnets are the strongest
magnets made. Some of them are strong enough to lift a train. A maglev train contains permanent magnets that are
repelled by strong electromagnets in the track. The force of repulsion causes the train to levitate above the track.
An electromagnet is stronger if there are more turns in the coil of wire or more current is flowing through it. A
bigger bar or one made of a material that is easier to magnetize also increases an electromagnet’s strength.
Questions
1. What is an electromagnet?
2. Why does an electromagnet have a stronger magnetic field than the solenoid it contains?
3. Identify four factors that affect the strength of an electromagnet.
5
1.2. Using Electromagnetism
Lesson 25.2: Multiple Choice
Name___________________ Class______________ Date__________
Circle the letter of the correct choice.
1. Each turn of the wire coil of a solenoid has
a.
b.
c.
d.
current that flows in a different direction.
a bar of iron inside of it.
its own magnetic field.
two of the above
2. You can increase the magnetic strength of a solenoid by
a.
b.
c.
d.
decreasing the amount of current flowing through it.
increasing the number of turns of wire in the coil.
attaching a compass to it.
two of the above
3. An electromagnet is stronger if it uses
a.
b.
c.
d.
less current.
a straight wire instead of a coil.
a smaller bar of ferromagnetic material.
a ferromagnetic material that is easier to magnetize.
4. Devices that contain electromagnets include
a.
b.
c.
d.
fans.
telephones.
CD players.
all of the above
5. Pressing the button of an electric doorbell causes two electric contacts to come together and
a.
b.
c.
d.
turn off an electromagnet.
push against a bell.
complete an electric circuit.
turn a shaft.
6. The electromagnet in an electric motor is located between
a.
b.
c.
d.
opposite poles of permanent magnets.
the commutator and shaft.
the voltage source and coil.
none of the above
7. In an electric motor, the shaft and the electromagnet both have
a.
b.
c.
d.
electrical energy.
kinetic energy.
a magnetic field.
a source of current.
Lesson 25.2: Matching
Name___________________ Class______________ Date________
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Chapter 1. Electromagnetism Worksheets
Match each definition with the correct term.
Definitions
_____ 1. device that uses an electromagnet to change electrical energy to kinetic energy
_____ 2. material such as iron that can be magnetized
_____ 3. part of an electric motor that changes the direction of the current
_____ 4. part of an electric motor that is turned by the rotating electromagnet
_____ 5. solenoid wrapped around a bar of ferromagnetic material
_____ 6. type of magnet that a solenoid resembles
_____ 7. coil of wire with electric current flowing through it, giving it a magnetic field
Terms
a. solenoid
b. ferromagnetic material
c. electromagnet
d. bar magnet
e. electric motor
f. shaft
g. commutator
Lesson 25.2: Fill in the Blank
Name___________________ Class______________ Date________
Fill in the blank with the appropriate term.
1.
2.
3.
4.
5.
6.
7.
The magnetic field of a coiled wire is __________ than the magnetic field around a straight wire.
The magnetic field of an electromagnetic magnetizes the iron bar inside it by aligning its __________.
The strongest magnets that are made are __________.
A solenoid with more turns of wire has a(n) __________ magnetic field.
Most electric devices that have moving parts contain __________.
The __________ inside a doorbell attracts the clapper and causes it to hit the bell.
The electromagnet inside an electric motor rotates because it is repelled by a(n) __________.
Lesson 25.2: Critical Writing
Name___________________ Class______________ Date________
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.
Explain how an electric motor changes electrical energy to kinetic energy.
7
1.3. Generating and Using Electricity
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1.3 Generating and Using Electricity
Lesson 25.3: True or False
Name___________________ Class______________ Date__________
Determine if the following statements are true or false.
_____ 1. Current will flow through a wire in a closed circuit whenever the wire crosses magnetic field lines.
_____ 2. Electromagnetic induction occurs when an electromagnet creates a magnetic field.
_____ 3. If you were to mechanically turn the shaft of an electric motor, the motor would generate electricity.
_____ 4. An electric generator contains a magnet and a rotating coil of wire.
_____ 5. An electric generator can produce only direct current.
_____ 6. A car generator uses the kinetic energy of a turning crankshaft.
_____ 7. A hydroelectric power plant uses the kinetic energy of steam under pressure.
_____ 8. An electric transformer works only with alternating current.
_____ 9. The iron core of an electric transformer becomes an electromagnet when current passes through the P coil.
_____ 10. The P and S coils of an electric transformer always have the same number of turns of wire.
Lesson 25.3: Critical Reading
Name___________________ Class______________ Date__________
Read this passage from the text and answer the questions that follow.
Electrifying the Home
Power plant generators produce high-voltage electric current. Many power plants also use step-up transformers to
increase the voltage of the current even more. By increasing the voltage, the amount of current traveling through
power lines is decreased. This results in less loss of electrical energy as the current travels from power plants to
homes. However, the voltage in power lines is too high to be safe for home circuits. The voltage in power lines may
be as great as 750,000 volts, whereas the voltage of most home circuits is 240 volts or less. One or more step-down
transformers decrease the voltage of current before it enters a house. Other step-down transformers within the house
lower the voltage of some of the home’s circuits.
Questions
1. Why is a step-up transformer used as electric current leaves a power plant?
2. Why is a step-down transformer needed before electric current enters a home?
8
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Chapter 1. Electromagnetism Worksheets
Lesson 25.3: Multiple Choice
Name___________________ Class______________ Date__________
Circle the letter of the correct choice.
1. What happens if a magnetic field and an electric conductor move relative to one another?
a.
b.
c.
d.
The magnetic field becomes stronger.
The conductor becomes an electromagnet.
The conductor becomes an electric insulator.
Electric current flows through the conductor.
2. Assume that a bar magnet is placed inside a coil of wire that is part of a closed circuit. Which situation
produces an alternating current in the wire?
a.
b.
c.
d.
The magnet is moved back and forth inside the coil.
The coil is moved back and forth over the magnet.
The magnet is connected to the closed circuit.
two of the above
3. You can create more current by moving the coil or magnet in question 2
a.
b.
c.
d.
slower.
faster.
farther.
none of the above
4. Devices that use electromagnetic induction include
a.
b.
c.
d.
electric motors.
electric generators.
electric transformers.
two of the above.
5. An electric generator uses kinetic energy to
a.
b.
c.
d.
rotate a coil of wire.
create a magnetic field.
reverse the poles of an electromagnet.
change the voltage of electric current.
6. When alternating current flows through coil P of an electric transformer, it
a.
b.
c.
d.
changes to direct current.
magnetizes an iron core.
repels a magnetic field.
charges a battery.
7. Increasing the voltage of current leaving a power plant causes the
a.
b.
c.
d.
amount of current to increase.
amount of current to decrease.
direction of current to change.
two of the above
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1.3. Generating and Using Electricity
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Lesson 25.3: Matching
Name___________________ Class______________ Date________
Match each definition with the correct term.
Definitions
_____ 1. process of generating electric current with a changing magnetic field
_____ 2. device that uses electromagnetic induction to increase the voltage of electric current
_____ 3. device in a power plant that provides kinetic energy to the electric generator
_____ 4. idea that a changing magnetic field produces an electric current
_____ 5. device that changes kinetic energy to electrical energy through electromagnetic induction
_____ 6. device that uses electromagnetic induction to decrease the voltage of electric current
_____ 7. device that measures the amount of current flowing through a wire
Terms
a. electric generator
b. ammeter
c. step-up transformer
d. turbine
e. electromagnetic induction
f. step-down transformer
g. Faraday’s law
Lesson 25.3: Fill in the Blank
Name___________________ Class______________ Date________
Fill in the blank with the appropriate term.
1.
2.
3.
4.
5.
6.
7.
If a magnet moves inside a coil of wire that is part of a circuit, it produces __________.
An electric generator is a(n) __________ in reverse.
The electric generator in a car produces __________ electric current.
A(n) __________ consists of two wire coils wrapped around an iron core.
In a step-down transformer, coil P has __________ turns of wire than coil S.
A power plant may use a(n) __________ to change the voltage of current before it travels to homes.
A(n) __________ is used to change the voltage of current from a power plant before it enters a home.
Lesson 25.3: Critical Writing
Name___________________ Class______________ Date________
Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.
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Chapter 1. Electromagnetism Worksheets
Explain why an electric transformer does not work with direct current.
11