Question 1

The ac motor and generator were invented by

Accepted Answer

A)  Edison. 
B)  Tesla. 
C)  Westinghouse. 
D)  Maxwell. 
E)  Hertz. 
A)  Edison. 
B)  Tesla. 
C)  Westinghouse. 
D)  Maxwell. 
E)  Hertz.

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 m T 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·m2 
A)  0.0 
B)  15 mT·m2 
C)  30 mT·m2 
D)  60 mT·m2 
E)  12 mT·m2

Question 3

A series LR circuit includes a 9.0 V battery,a resistance of 0.20 $\Omega$,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 mH 
A)  42 mH 
B)  15 mH 
C)  32 mH 
D)  40 mH 
E)  22 mH

Question 4

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)  $\pi$ lines/m2. 
A)  1 V·m. 
B)  1 V·s / A. 
C)  1 T·m2. 
D)  $\pi$ lines/m2.

Question 5

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 6

What is the inductance of a coil that has an emf of 0.82 V induced in it while the current through it is changing at 2.0 A/s?

Accepted Answer

A)  3.3 H 
B)  33 mH 
C)  1.6 H 
D)  41 mH 
E)  0.41 H 
A)  3.3 H 
B)  33 mH 
C)  1.6 H 
D)  41 mH 
E)  0.41 H

Question 7

A series LR circuit includes a 9.0 V battery,a resistance of 0.50 $\Omega$,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 8

A coiled loop of wire is in the field region between the pole tips of an electromagnet.Which of the following things would NOT result in an induced EMF in the coil?

Accepted Answer

A)  Rotation of the coil 
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. 
A)  Rotation of the coil 
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.

Question 9

In a transformer,the relationship between the primary and secondary currents depends on all of the following quantities except:

Accepted Answer

A)  the number of turns the primary and secondary windings have 
B)  the resistance of the windings 
C)  the voltage in the primary winding 
D)  the properties of the core material 
A)  the number of turns the primary and secondary windings have 
B)  the resistance of the windings 
C)  the voltage in the primary winding 
D)  the properties of the core material

Question 10

A metal rod of length L moves with velocity v,perpendicular to its length,in a magnetic field B,which is perpendicular to both the rod and its velocity.If the length of the rod is doubled,what happens to the electric field in the rod?

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 11

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 12

What electric field has the same energy density as a 1.0 T magnetic field?

Accepted Answer

A)  1.0 V/m 
B)  3.0 $\times$ 108 V/m 
C)  9.0 $\times$ 1016 V/m 
D)  1.1 $\times$ 10-17 V/m 
E)  3.3 $\times$ 10-9 V/m 
A)  1.0 V/m 
B)  3.0 $\times$ 108 V/m 
C)  9.0 $\times$ 1016 V/m 
D)  1.1 $\times$ 10-17 V/m 
E)  3.3 $\times$ 10-9 V/m

Question 13

The emf produced by an ac generator is given by $\varepsilon$ = $\omega$NBA sin $\omega$t.In the SI system,what is the value of $\omega$ for a frequency of 60.0 Hz?

Accepted Answer

A)  60.0 Hz 
B)  120 rad/s 
C)  2.00 $\pi$ rad/s 
D)  377 rad/s 
E)  377 Hz 
A)  60.0 Hz 
B)  120 rad/s 
C)  2.00 $\pi$ rad/s 
D)  377 rad/s 
E)  377 Hz

Question 14

A loop of wire is moved through a region of uniform magnetic field.As it is moved,its orientation with respect to the magnetic field direction does not change.The induced current at this time in the loop:

Accepted Answer

A)  depends on the shape of the loop 
B)  depends on the magnitude of the field 
C)  depends on the speed with which it is moved 
D)  is zero 
E)  depends on the acceleration of the loop 
A)  depends on the shape of the loop 
B)  depends on the magnitude of the field 
C)  depends on the speed with which it is moved 
D)  is zero 
E)  depends on the acceleration of the loop

Exam 20: Electromagnetic Induction

The ac motor and generator were invented by

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 m T magnetic field is perpendicular to both the rod and its velocity.What is the magnetic flux swept through per second by the rod?

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

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

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

What is the inductance of a coil that has an emf of 0.82 V induced in it while the current through it is changing at 2.0 A/s?

A series LR circuit includes a 9.0 V battery,a resistance of 0.50 Ω\OmegaΩ ,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 coiled loop of wire is in the field region between the pole tips of an electromagnet.Which of the following things would NOT result in an induced EMF in the coil?

In a transformer,the relationship between the primary and secondary currents depends on all of the following quantities except:

A metal rod of length L moves with velocity v,perpendicular to its length,in a magnetic field B,which is perpendicular to both the rod and its velocity.If the length of the rod is doubled,what happens to the electric field in the rod?

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?

What electric field has the same energy density as a 1.0 T magnetic field?

The emf produced by an ac generator is given by ε\varepsilonε = ω\omegaω NBA sin ω\omegaω t.In the SI system,what is the value of ω\omegaω for a frequency of 60.0 Hz?

A loop of wire is moved through a region of uniform magnetic field.As it is moved,its orientation with respect to the magnetic field direction does not change.The induced current at this time in the loop:

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Filters

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

A series LR circuit includes a 9.0 V battery,a resistance of 0.50 $\Omega$ ,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?

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?

The emf produced by an ac generator is given by $\varepsilon$ = $\omega$ NBA sin $\omega$ t.In the SI system,what is the value of $\omega$ for a frequency of 60.0 Hz?