1. Magnetism Preview Understanding Concepts Reading Skills
Interpreting Graphics

2. Understanding Concepts
1. A straight vertical wire is carrying an electric current. Positive charges are flowing straight down. What is the direction of the magnetic field generated by the wire as viewed from above?
A. straight up
B. straight down
C. clockwise
D. counterclockwise

3. Understanding Concepts, continued
1. A straight vertical wire is carrying an electric current. Positive charges are flowing straight down. What is the direction of the magnetic field generated by the wire as viewed from above?
A. straight up
B. straight down
C. clockwise
D. counterclockwise

4. Understanding Concepts, continued
2. What type of device is used to measure the current in an electromagnet?
F. an electric motor
G. a galvanometer
H. a generator
I. a solenoid

5. Understanding Concepts, continued
2. What type of device is used to measure the current in an electromagnet?
F. an electric motor
G. a galvanometer
H. a generator
I. a solenoid

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3. A charged particle is moving through a magnetic field. In which direction is the particle moving when the magnetic force acting on the particle is at its greatest?
A. in the same direction as the magnetic field lines
B. in the opposite direction from the magnetic
field lines
C. at right angles to the magnetic field lines
D. clockwise around the magnetic field lines

7. Understanding Concepts, continued
3. A charged particle is moving through a magnetic field. In which direction is the particle moving when the magnetic force acting on the particle is at its greatest?
A. in the same direction as the magnetic field lines
B. in the opposite direction from the magnetic
field lines
C. at right angles to the magnetic field lines
D. clockwise around the magnetic field lines

8. Understanding Concepts, continued
4. In an AC generator, a loop of wire rotates between two magnetic poles. At what angle(s) of rotation relative to the magnet does the loop generate the most current?
F. 0˚ and 180˚
G. 90˚ and 270˚
H. 180˚
I. 360˚

9. Understanding Concepts, continued
4. In an AC generator, a loop of wire rotates between two magnetic poles. At what angle(s) of rotation relative to the magnet does the loop generate the most current?
F. 0˚ and 180˚
G. 90˚ and 270˚
H. 180˚
I. 360˚

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5. How would a compass located precisely at the Earth’s geographic north pole behave?

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5. How would a compass located precisely at the Earth’s geographic north pole behave?
Answer: It would point toward the magnetic north pole.

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6. What is the difference between a solenoid and
an electromagnet?

13. Understanding Concepts, continued
6. What is the difference between a solenoid and
an electromagnet?
Answer: An electromagnet is a solenoid with a metal rod through the center of the coil.

14. Reading Skills GETTING IT ON TAPE
Magnetic tape consists of a thin plastic strip bonded to a coating of ferric oxide powder. The ferric oxide, Fe2O3, makes the tape magnetizable. Early tape recorders were first developed in Germany and Britain. The first tape recorder used by the British Broadcasting Corporation in 1932 was a huge machine. It used steel razor tape that was 3 mm wide and 0.08 mm thick. The tape had to be run at 90 m/min, so the length of tape required for a half-hour program was nearly 3 km long, and a full reel had a mass of 25 kg. Furthermore, the quality of the sound experienced considerable degradation in the recording and playback process.

15. Reading Skills, continued
GETTING IT ON TAPE, continued
Higher-quality sound recording was developed in Germany during the late 1930s. During World War II, the Allies became aware of German radio broadcasts that seemed to be recorded. However, the audio quality and duration of the recordings were far greater than Allied technology would allow. At the end of the war, the Allies captured a number of German Magnetophon recorders from Radio Luxembourg, and commercial-quality magnetic recording entered the English-speaking world.
7. How is a tape coated with Fe2O3 similar to a
steel wire?

16. Reading Skills, continued
7. How is a tape coated with Fe2O3 similar to a
steel wire?
Answer: Both form lines of aligned magnetizable particles.

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8. Was the sound of a British recording during World War II better or worse after the recording was played?

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8. Was the sound of a British recording during World War II better or worse after the recording was played?
Answer: Worse

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9. The Allies captured recording devices called
magnetophons. Why is this name appropriate?

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9. The Allies captured recording devices called
magnetophons. Why is this name appropriate?
Answer: Magnetophon is appropriate because it means “sound from magnetism.”

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10. Why would bringing audiotape near a powerful
magnet be a bad idea?

22. Reading Skills, continued
10. Why would bringing audiotape near a powerful
magnet be a bad idea?
Answer: The magnetizable particles will align with the magnet, erasing the tape.

23. Interpreting Graphics
The diagram below shows an electric circuit that includes a solenoid. Use this diagram to answer questions 11–12.
11. What is the direction of the magnetic field at point X due to the current in section EF?
A. into the page
B. out of the page
C. to the left
D. to the right

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11. What is the direction of the magnetic field at point X due to the current in section EF?
A. into the page
B. out of the page
C. to the left
D. to the right

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12. To which point is the north pole of the solenoid the closest?
F. A
G. B
H. C
I. D

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12. To which point is the north pole of the solenoid the closest?
F. A
G. B
H. C
I. D

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The following graphic shows four bar magnets and the magnetic fields that they generate. Use this graphic to answer questions 13–14.
13. Suppose that A and E are the north poles of their magnets. What other points have a north polarity?
A. B and G
B. C and H
C. D and G
D. D and H

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13. Suppose that A and E are the north poles of their magnets. What other points have a north polarity?
A. B and G
B. C and H
C. D and G
D. D and H

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14. Which two magnets could combine their magnetic fields into one long magnet without being rotated? What would happen to their poles?

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14. Which two magnets could combine their magnetic fields into one long magnet without being rotated? What would happen to their poles?
Answer: The upper magnets could combine by connecting points B and C; B and C would lose polarity and A and D would become the poles of the new magnet.