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Transcript
Name: ________________________ Class: ___________________ Date: __________
ID: A
Chapter 22 Multi-format Test
Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.
____
1. The unit used to measure the strength of a magnetic field is the ohm. _________________________
____
2. As the distance between two magnets increases, the force between their magnetic fields decreases.
_________________________
____
3. Earth’s core acts as a permanent magnetic in producing Earth’s magnetic field.
_________________________
____
4. A generator changes electrical energy to mechanical energy. __________________________
____
5. The rotating element of a motor is referred to as the field coil. _________________________
Completion
Complete each statement.
Select the correct term to complete each sentence. There are extra terms in the list.
north
attract
permanent
generator
magnet
repel
electromagnet
electric motor
south
field
induction
alternating
6. The influence created by a magnet that exerts forces on other magnets is called a magnetic
____________________.
7. If two opposite poles of magnets are facing each other, the magnets will ____________________ one
another.
8. Earth’s core is surrounded by a magnetic field aligned so that its magnetic south pole is located near its
geographic ____________________ pole.
9. In ____________________ magnets, the magnetic fields of individual atoms are aligned in a similar
direction.
10. Electromagnetic ______________________________ occurs when current is induced in a wire by a moving
magnet.
11. A device that changes mechanical energy to electrical energy is a ____________________.
12. The current produced by a generator is always ____________________ current.
Short Answer
13. Is it possible to have a magnet with only a north pole? Explain.
14. What two pieces of information can you get from a magnetic field diagram?
1
Name: ________________________
ID: A
15. The forces between two magnets depend upon the magnets’ alignment. Explain how to cause attractive and
repulsive forces between two magnets.
16. Several compasses are placed around a bar magnet. Which end of the magnet is its north pole?
17. In this diagram of Earth’s magnetic field, where is the magnetic field the strongest?
18. A strong magnet and a weak magnet are placed north pole to south pole and are attracted to each other with a
magnetic force. Which magnet has the stronger force?
19. Describe how to make an electromagnet.
20. Name two ways to increase the strength of an electromagnet.
21. What happens when you place a compass near a current-carrying wire?
22. Name 3 devices that use electromagnets in their operation.
23. Strong electromagnets are used in junk yards for moving large pieces of iron from place to place. What is the
advantage in using an electromagnet instead of a large permanent magnet?
24. What is the purpose of a commutator in an electric motor?
25. A bar magnet is suspended so that it is free to rotate. When you hold a second bar magnet near the suspended
magnet, the suspended magnet begins to rotate. Explain what must be done to keep the magnet rotating.
2
Name: ________________________
ID: A
26. How can you induce current in a wire using a permanent magnet?
Problem
27. In which direction will the rotating disk spin?
Essay
28. Explain how an electric motor works. Be sure to use the words rotor, commutator, permanent magnets,
and electromagnets.
Other
The diagram represents an iron nail wrapped with a current carrying wire.
Figure 22-1
29. What type of device does Figure 22-1 represent?
30. Label the pointed end and the head of the nail in Figure 22-1 with an “N” and “S” to represent the magnetic
north and south poles of the nail.
3
ID: A
Chapter 22 Multi-format Test
Answer Section
MODIFIED TRUE/FALSE
1. ANS: F, gauss
DIF: basic
REF: section 22.1
2. ANS: T
3. ANS: F, electromagnet
DIF: basic
DIF: basic
REF: section 22.1
4. ANS: F, electric motor
DIF: basic
5. ANS: F, armature
DIF:
basic
REF: section 22.3
REF: section 22.3
COMPLETION
6. ANS: field
DIF: basic
7. ANS: attract
REF: section 22.1
DIF: basic
8. ANS: north
REF: section 22.1
DIF: intermediate
9. ANS: permanent
REF: section 22.1
DIF: basic
10. ANS: induction
REF: section 22.2
DIF: basic
11. ANS: generator
REF: section 22.3
DIF: basic
12. ANS:
alternating
AC
REF: section 22.3
DIF:
intermediate
REF: section 22.3
1
REF: section 22.1
ID: A
SHORT ANSWER
13. ANS:
No. All magnets have two opposite poles, north and south. It is impossible to have only a north or south pole
by itself.
DIF: basic
REF: section 22.1
14. ANS:
The direction and the relative strength of the magnetic field
DIF: intermediate REF: section 22.1
15. ANS:
Attractive forces exist between two magnets when unlike poles face each other. Repulsive forces exist when
like poles are facing on another.
DIF: intermediate
16. ANS:
B
REF: section 22.1
DIF: intermediate REF: section 22.1
17. ANS:
At point B. The field is strongest at the north or south magnetic poles, not at the north or south geographic
poles.
DIF: advanced
REF: section 22.1
18. ANS:
According to Newton’s third law, they exert the same force on each other.
DIF: advanced
REF: section 22.1
19. ANS:
Electromagnets are magnets created when there is electric current flowing in a wire. The simplest
electromagnet uses a coil of wire that must be wrapped around a piece of metal. Iron is often used. Because
iron is magnetic, it concentrates the magnetic field created by the current in the coil.
DIF: basic
REF: section 22.2
20. ANS:
Any two of these three answers is correct:
Increase current flow in the wire, increase amount of iron/steel in the core, increase the number of turns of
wire in the coil.
DIF: basic
REF: section 22.2
21. ANS:
The compass needle moves as if the wire were a magnet.
DIF:
intermediate
REF: section 22.2
2
ID: A
22. ANS:
Answers may vary. Correct answers include:
Doorbells, speakers, microphones, motors, toasters, maglev trains
DIF: intermediate REF: section 22.2
23. ANS:
Once the permanent magnet is attracted to the heavy metal piece, it would be difficult to free the metal from
the magnet. The electromagnet will lose its magnetism when the current is turned off.
DIF: advanced
REF: section 22.2
24. ANS:
The commutator switches the polarity of the electromagnet from north to south and back again. Switching the
polarity makes the rotor turn.
DIF: basic
REF: section 22.3
25. ANS:
To keep the magnet spinning, you need to reverse the hand-held magnet as each end of the suspended magnet
comes by.
DIF: intermediate REF: section 22.3
26. ANS:
You can induce current either by moving the permanent magnet through a coil of wire or by moving a coil of
wire over the permanent magnet.
DIF:
intermediate
REF: section 22.3
PROBLEM
27. ANS:
Counterclockwise
DIF:
intermediate
REF: section 22.3
ESSAY
28. ANS:
A motor has a spinning disk called a rotor. When the rotor is spinning, the motor can do useful work. The
rotor has magnets along its outside edge. In some motors, these are permanent magnets. Other motors use
electromagnets. Outside the rotor there is another magnet (or set of magnets). A commutator causes the
magnet to reverse its polarity from north to south and back again. As the polarity changes, the magnets in the
rotor are first attracted and then repelled by the “outer” magnet. This action is similar to the
pull-and-then-push action that we use to turn a merry-go-round. The attracting and repelling action of the
“outer” magnet causes the rotor to turn..
DIF:
intermediate
REF: section 22.3
3
ID: A
OTHER
29. ANS:
It represents an electromagnet.
DIF: basic
REF: section 22.2
30. ANS:
N at the “head” and S at the “point”
DIF:
advanced
REF: section 22.2
4
Chapter 22 Multi-format Test [Answer Strip]
F
_____
1.
T
_____
2.
F
_____
3.
F
_____
4.
F
_____
5.
ID: A