Question 1

A solenoid of length 2.8 cm and diameter 0.75 cm is wound with 160 turns per cm. When the current through the solenoid is 0.20 A, what is the magnetic flux through one of the windings of the solenoid?

Accepted Answer

A)   2.5 × 10-7 Wb
B)   1.8 × 10-7 Wb
C)   0.88 × 10-7 Wb
D)   1.2 × 10-7 WbE) C) and D)
F) None of the above

Question 2

A metal rod of length 2.0 m is moved at 6.0 m/s in a direction perpendicular to its length. A 5.0 mT magnetic field is perpendicular to both the rod and its velocity. What is the magnitude of the electric field in the rod?

Accepted Answer

A)   12 mV/m
B)   60 mV/m
C)   30 mV/m
D)   15 mV/m
E)   0.0 mV/mF) None of the above
G) A) and D)

Question 3

What is the magnetic energy stored by a 300 mH inductor with a 2.0 A current going through it?

Accepted Answer

A)   0.60 J
B)   1.2 J
C)   30 mJ
D)   0.15 J
E)   0.075 JF) A) and E)
G) None of the above

Question 4

An LR circuit is prepared for an experiment, initially with its switch open. The time constant is that time after switch closure at which the current reaches approximately what percentage of its final value?

Accepted Answer

A)   100%
B)   90%
C)   37%
D)   63%
E)   50%F) A) and D)
G) C) and E)

Question 5

A metal rod of length 2.0 m is moved at 6.0 m/s in a direction perpendicular to its length. A 5.0 mT magnetic field is perpendicular to both the rod and its velocity. What is the magnetic flux swept through per second by the rod?

Accepted Answer

A)   0.0
B)   15 mT·m2
C)   30 mT·m2
D)   60 mT·m2
E)   12 mT·m2F) A) and B)
G) B) and E)

Question 6

The north end of a bar magnet is pushed downward toward a wire loop in the plane of the paper. In which direction is the induced current, and which way is the induced magnetic field?

Accepted Answer

A)   clockwise, into the paper
B)   clockwise, out of the paper
C)   counter-clockwise, into the paper
D)   counter-clockwise, out of the paper
E)   There is no induced current.F) None of the above
G) D) and E)

Question 7

A coil is rotated in a magnetic field about an axis perpendicular to both the field and the coil axis (normal to the coil area) . During each rotation, how many times does the flux through the coil equal zero?

Accepted Answer

A)   0
B)   1
C)   2
D)   4
E)   more than 4F) All of the above
G) B) and E)

Question 8

The induced emf in a straight segment of wire that moves through a region with a magnetic field depends on all of the following, except

Accepted Answer

A)   the orientation of the wire with respect to the magnetic field direction.
B)   the length of the wire.
C)   the resistance of the wire.
D)   speed of the wire.
E)   the magnetic field strength.F) C) and E)
G) A) and C)

Question 9

A metal rod of length 2.0 m is moved at 6.0 m/s in a direction perpendicular to its length. A 5.0 mT magnetic field is perpendicular to both the rod and its velocity. If the resistance of the rod is 15 mΩ, what is the current in the rod?

Accepted Answer

A)   0.0 A
B)   1.0 A
C)   2.0 A
D)   4.0 A
E)   8.0 AF) C) and D)
G) A) and B)

Question 10

A 33 mH inductor has a current going through it that is increasing at a rate of 2.3 A/s. What is the magnitude of the induced emf in this coil?

Accepted Answer

A)   33 mV
B)   76 mV
C)   13 mV
D)   95 mV
E)   2.5 VF) B) and E)
G) B) and D)

Question 11

A transformer has 200 turns on its primary and 12 turns on its secondary. If the input voltage is 2000 V, what is the output voltage?

Accepted Answer

A)   3.3 × 104 V
B)   240 V
C)   170 V
D)   120 V
E)   100 VF) None of the above
G) A) and D)

Question 12

A generator is designed to produce a maximum emf of 170 V while rotating at 3200 rpm. The 1531 coils of the generator are circular with diameter 7.5 cm. What is the necessary magnetic field for the generator?

Accepted Answer

A)   0.0079 T
B)   0.30 T
C)   0.075 T
D)   0.24 TE) A) and C)
F) C) and D)

Question 13

The SI unit H (the henry)  is equal to a

Accepted Answer

A)   V/m.
B)   V/A.
C)   V·s.
D)   V·s/A.
E)   V·A/s.F) A) and B)
G) A) and C)

Question 14

A series LR circuit includes a 9.0 V battery, a resistance of 0.20 Ω, and an inductor. When the switch is closed, the circuit exhibits a time constant of 200 ms. What is the inductance of the circuit?

Accepted Answer

A)   42 mH
B)   15 mH
C)   32 mH
D)   40 mH
E)   22 mHF) A) and D)
G) A) and C)

Question 15

After the switch is closed in a series LR circuit, what is the current when a time equal to four time constants has elapsed?

Accepted Answer

A)   (1/5)  Imax
B)   (15/16)  Imax
C)   (1/16)  Imax
D)   0.018 Imax
E)   0.98 ImaxF) C) and E)
G) A) and E)

Question 16

A horizontal desk surface measures 1.3 m by 1.0 m. If the Earth's magnetic field has a magnitude of 0.44 mT and is directed 65° below the horizontal, what is the magnetic flux through the desk surface?

Accepted Answer

A)   1.1 × 10-3 Wb
B)   5.2 × 10-4 Wb
C)   3.2 × 10-4 Wb
D)   7.3 × 10-3 WbE) A) and C)
F) B) and C)

Question 17

A 20 turn coil of area 10 cm2 is placed in a magnetic field so that the normal to the coil's area is in the same direction as the field. If the magnitude of the field increases from 0.25 T to 0.35 T in 2.0 s, what is the average emf induced in the coil?

Accepted Answer

A)   7.0 mV
B)   2.0 mV
C)   1.0 mV
D)   3.5 mV
E)   4.0 mVF) B) and D)
G) A) and B)

Question 18

A coiled loop of wire is in the field region between the poles of an electromagnet, with the axis of the coil aligned with the magnetic field. Which of the following things would NOT result in an induced EMF in the coil?

Accepted Answer

A)   Rotation of the coil about an axis perpendicular to the coil axis
B)   Pulling the coil partly out of the field region
C)   Increasing or decreasing the current in the electromagnet
D)   Flexing the coil and changing its shape, keeping the perimeter the same
E)   None of these choices will work.F) A) and B)
G) A) and C)

Question 19

A series LR circuit includes a 9.0 V battery, a resistance of 0.50 Ω, and an inductance of 0.80 H. What is the energy stored by the inductor 2.0 s after the switch is closed?

Accepted Answer

A)   33 mJ
B)   30 mJ
C)   13 J
D)   66 J
E)   33 JF) B) and E)
G) A) and E)

Question 20

A 1.7 H inductor has a current of 6.6 A flowing through it. The current reduces to 3.3 A over a period of 1.6 s. What is the average power the inductor supplies to the circuit as the current reduces?

Accepted Answer

A)   17 W
B)   37 W
C)   9.3 W
D)   28 W
E)   46 WF) D) and E)
G) B) and D)

Exam 20: Electromagnetic Induction

An LR circuit is prepared for an experiment, initially with its switch open. The time constant is that time after switch closure at which the current reaches approximately what percentage of its final value?

Correct AnswerverifiedShow Answer

A transformer has 200 turns on its primary and 12 turns on its secondary. If the input voltage is 2000 V, what is the output voltage?

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A generator is designed to produce a maximum emf of 170 V while rotating at 3200 rpm. The 1531 coils of the generator are circular with diameter 7.5 cm. What is the necessary magnetic field for the generator?

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After the switch is closed in a series LR circuit, what is the current when a time equal to four time constants has elapsed?

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A metal rod of length 2.0 m is moved at 6.0 m/s in a direction perpendicular to its length. A 5.0 mT magnetic field is perpendicular to both the rod and its velocity. If the resistance of the rod is 15 mΩ, what is the current in the rod?

Correct AnswerverifiedShow Answer

A 20 turn coil of area 10 cm2 is placed in a magnetic field so that the normal to the coil's area is in the same direction as the field. If the magnitude of the field increases from 0.25 T to 0.35 T in 2.0 s, what is the average emf induced in the coil?

Correct AnswerverifiedShow Answer

A series LR circuit includes a 9.0 V battery, a resistance of 0.50 Ω, and an inductance of 0.80 H. What is the energy stored by the inductor 2.0 s after the switch is closed?

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A 1.7 H inductor has a current of 6.6 A flowing through it. The current reduces to 3.3 A over a period of 1.6 s. What is the average power the inductor supplies to the circuit as the current reduces?

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A metal rod of length 2.0 m is moved at 6.0 m/s in a direction perpendicular to its length. A 5.0 mT magnetic field is perpendicular to both the rod and its velocity. What is the magnetic flux swept through per second by the rod?

Correct AnswerverifiedShow Answer

A coiled loop of wire is in the field region between the poles of an electromagnet, with the axis of the coil aligned with the magnetic field. Which of the following things would NOT result in an induced EMF in the coil?

Correct AnswerverifiedShow Answer

A horizontal desk surface measures 1.3 m by 1.0 m. If the Earth's magnetic field has a magnitude of 0.44 mT and is directed 65° below the horizontal, what is the magnetic flux through the desk surface?

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A series LR circuit includes a 9.0 V battery, a resistance of 0.20 Ω, and an inductor. When the switch is closed, the circuit exhibits a time constant of 200 ms. What is the inductance of the circuit?

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The induced emf in a straight segment of wire that moves through a region with a magnetic field depends on all of the following, except

Correct AnswerverifiedShow Answer

A 33 mH inductor has a current going through it that is increasing at a rate of 2.3 A/s. What is the magnitude of the induced emf in this coil?

Correct AnswerverifiedShow Answer

What is the magnetic energy stored by a 300 mH inductor with a 2.0 A current going through it?

Correct AnswerverifiedShow Answer

The north end of a bar magnet is pushed downward toward a wire loop in the plane of the paper. In which direction is the induced current, and which way is the induced magnetic field?

Correct AnswerverifiedShow Answer

The SI unit H (the henry) is equal to a

Correct AnswerverifiedShow Answer

A solenoid of length 2.8 cm and diameter 0.75 cm is wound with 160 turns per cm. When the current through the solenoid is 0.20 A, what is the magnetic flux through one of the windings of the solenoid?

Correct AnswerverifiedShow Answer

A coil is rotated in a magnetic field about an axis perpendicular to both the field and the coil axis (normal to the coil area) . During each rotation, how many times does the flux through the coil equal zero?

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A metal rod of length 2.0 m is moved at 6.0 m/s in a direction perpendicular to its length. A 5.0 mT magnetic field is perpendicular to both the rod and its velocity. What is the magnitude of the electric field in the rod?

Correct AnswerverifiedShow Answer

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A 20 turn coil of area 10 cm² is placed in a magnetic field so that the normal to the coil's area is in the same direction as the field. If the magnitude of the field increases from 0.25 T to 0.35 T in 2.0 s, what is the average emf induced in the coil?

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