Question 1

The unit of magnetic flux is the weber. 1 Wb equals

Accepted Answer

A)  1 V·m. 
B)  1 V·s/A. 
C)  1 T·m2. 
D)  π lines/m2. 
A)  1 V·m. 
B)  1 V·s/A. 
C)  1 T·m2. 
D)  π lines/m2.

Question 2

An inductor has 200 turns/cm and a cross-sectional area of 1.8 cm2. If its inductance is 32 mH, what is its length?

Accepted Answer

A)  21 cm 
B)  15 cm 
C)  35 cm 
D)  64 cm 
E)  72 cm 
A)  21 cm 
B)  15 cm 
C)  35 cm 
D)  64 cm 
E)  72 cm

Question 3

If the magnetic energy stored by a 0.50 H inductor is 3.6 J, what is the current through it?

Accepted Answer

A)  0.13 A 
B)  0.90 A 
C)  1.8 A 
D)  3.8 A 
E)  5.4 A 
A)  0.13 A 
B)  0.90 A 
C)  1.8 A 
D)  3.8 A 
E)  5.4 A

Question 4

A generator has 200 turns of wire on a coil of radius 2.00 cm. What rotational speed is necessary to produce an emf of amplitude 4.50 V if the magnetic field in the region of the coil is 0.180 T?

Accepted Answer

A)  60.0 rad/s 
B)  16.0 rpm 
C)  100 rpm 
D)  500 rpm 
E)  950 rpm 
A)  60.0 rad/s 
B)  16.0 rpm 
C)  100 rpm 
D)  500 rpm 
E)  950 rpm

Question 5

An ideal solenoid has a length of 25 mm. If the windings are compressed so that the length is reduced to ½ of its original length how does the inductance change?

Accepted Answer

A)  ¼ of original 
B)  to ½ of original 
C)  twice the original 
D)  quadruple the original 
A)  ¼ of original 
B)  to ½ of original 
C)  twice the original 
D)  quadruple the original

Question 6

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 potential difference between the ends of the rod?

Accepted Answer

A)  12 mV 
B)  60 mV 
C)  30 mV 
D)  15 mV 
E)  0 mV 
A)  12 mV 
B)  60 mV 
C)  30 mV 
D)  15 mV 
E)  0 mV

Question 7

Suppose an emf is induced in a loop of wire by rotating the loop in a magnetic field. If the diameter of the loop were twice as large, how would the induced emf compare?

Accepted Answer

A)  The induced emf would be 4 times as much. 
B)  The induced emf would be twice as much. 
C)  There would be no change in the induced emf. 
D)  The induced emf would be 6.28 times as much. 
A)  The induced emf would be 4 times as much. 
B)  The induced emf would be twice as much. 
C)  There would be no change in the induced emf. 
D)  The induced emf would be 6.28 times as much.

Question 8

A series LR circuit includes a 9.0 V battery, a resistance of 0.50 Ω, and an inductance of 0.80 H. When the switch is closed, how long does it take for the current to reach one half of its maximum value?

Accepted Answer

A)  0.80 s 
B)  1.6 s 
C)  2.3 s 
D)  1.1 s 
E)  0.55 s 
A)  0.80 s 
B)  1.6 s 
C)  2.3 s 
D)  1.1 s 
E)  0.55 s

Question 9

A transformer with a turns ratio of 20/1 is used to step down the standard 170 V amplitude ac line voltage. What is the peak voltage in the secondary?

Accepted Answer

A)  6.0 V 
B)  7.3 V 
C)  170 V 
D)  8.5 V 
A)  6.0 V 
B)  7.3 V 
C)  170 V 
D)  8.5 V

Question 10

The ac motor and generator were invented by

Accepted Answer

A)  Thomas Edison. 
B)  Nikola Tesla. 
C)  George Westinghouse. 
D)  James Clerk Maxwell. 
E)  Heinrich Hertz. 
A)  Thomas Edison. 
B)  Nikola Tesla. 
C)  George Westinghouse. 
D)  James Clerk Maxwell. 
E)  Heinrich Hertz.

Question 11

If the rotation rate of a generator coil is doubled, what happens to the peak emf?

Accepted Answer

A)  It stays the same. 
B)  It doubles. 
C)  It quadruples. 
D)  It halves. 
E)  It quarters. 
A)  It stays the same. 
B)  It doubles. 
C)  It quadruples. 
D)  It halves. 
E)  It quarters.

Question 12

A flat coil has a maximum flux of 4.0 × 10-3 T·m2 through it, with its area perpendicular to a uniform magnetic field. When the coil is rotated 60° (so that its normal makes a 60° angle with the field), what is the flux through it?

Accepted Answer

A)  4.0 × 10-3 T·m2 
B)  8.0 × 10-3 T·m2 
C)  3.5 × 10-3 T·m2 
D)  2.0 × 10-3 T·m2 
E)  6.9 × 10-3 T·m2 
A)  4.0 × 10-3 T·m2 
B)  8.0 × 10-3 T·m2 
C)  3.5 × 10-3 T·m2 
D)  2.0 × 10-3 T·m2 
E)  6.9 × 10-3 T·m2

Question 13

If the number of turns on a transformer input is greater than the number on the output, then the transformer

Accepted Answer

A)  outputs greater voltage than at the input. 
B)  outputs less current than at the input. 
C)  outputs greater voltage and current than at the input. 
D)  outputs less voltage than at the input. 
E)  increases the voltage but does not affect the current. 
A)  outputs greater voltage than at the input. 
B)  outputs less current than at the input. 
C)  outputs greater voltage and current than at the input. 
D)  outputs less voltage than at the input. 
E)  increases the voltage but does not affect the current.

Question 14

An ideal transformer has an input voltage of 20,000 V and an output voltage of 260 V. If the input current is 26.0 A, what is the output current?

Accepted Answer

A)  1.70 A 
B)  10.0 A 
C)  100 A 
D)  200 A 
E)  2000 A 
A)  1.70 A 
B)  10.0 A 
C)  100 A 
D)  200 A 
E)  2000 A

Exam 20: Electromagnetic Induction

The unit of magnetic flux is the weber. 1 Wb equals

An inductor has 200 turns/cm and a cross-sectional area of 1.8 cm2. If its inductance is 32 mH, what is its length?

If the magnetic energy stored by a 0.50 H inductor is 3.6 J, what is the current through it?

A generator has 200 turns of wire on a coil of radius 2.00 cm. What rotational speed is necessary to produce an emf of amplitude 4.50 V if the magnetic field in the region of the coil is 0.180 T?

An ideal solenoid has a length of 25 mm. If the windings are compressed so that the length is reduced to ½ of its original length how does the inductance change?

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 potential difference between the ends of the rod?

Suppose an emf is induced in a loop of wire by rotating the loop in a magnetic field. If the diameter of the loop were twice as large, how would the induced emf compare?

A series LR circuit includes a 9.0 V battery, a resistance of 0.50 Ω, and an inductance of 0.80 H. When the switch is closed, how long does it take for the current to reach one half of its maximum value?

A transformer with a turns ratio of 20/1 is used to step down the standard 170 V amplitude ac line voltage. What is the peak voltage in the secondary?

The ac motor and generator were invented by

If the rotation rate of a generator coil is doubled, what happens to the peak emf?

A flat coil has a maximum flux of 4.0 × 10-3 T·m2 through it, with its area perpendicular to a uniform magnetic field. When the coil is rotated 60° (so that its normal makes a 60° angle with the field), what is the flux through it?

If the number of turns on a transformer input is greater than the number on the output, then the transformer

An ideal transformer has an input voltage of 20,000 V and an output voltage of 260 V. If the input current is 26.0 A, what is the output current?

Introduction

Motion Along a Line

Motion in a Plane

Force and Newtons Laws of Motion

Circular Motion

Conservation of Energy

Linear Momentum

Torque and Angular Momentum

Fluids

Elasticity and Oscillations

Waves

Sound

Temperature and the Ideal Gas

Heat

Thermodynamics

Electric Forces and Fields

Electric Potential

Electric Current and Circuits

Magnetic Forces and Fields

Alternating Current

Electromagnetic Waves

Reflection and Refraction of Light

Optical Instruments

Interference and Diffraction

Relativity

Early Quantum Physics and the Photon

Quantum Physics

Nuclear Physics

Particle Physics

Filters

An inductor has 200 turns/cm and a cross-sectional area of 1.8 cm². If its inductance is 32 mH, what is its length?

A flat coil has a maximum flux of 4.0 × 10^-3 T·m² through it, with its area perpendicular to a uniform magnetic field. When the coil is rotated 60^° (so that its normal makes a 60^° angle with the field), what is the flux through it?