Question 1

The quantity (B2/$\mu$o) has units of:

Accepted Answer

A)  J 
B)  J/H 
C)  J/m 
D)  J/m3 
E)  H/m3 
A)  J 
B)  J/H 
C)  J/m 
D)  J/m3 
E)  H/m3

Question 2

A 3.5 mH inductor and a 4.5 mH inductor are connected in series. The equivalent inductance is:

Accepted Answer

A)  2.0 mH 
B)  0.51 mH 
C)  0.13 mH 
D)  1.0 mH 
E)  8.0 mH 
A)  2.0 mH 
B)  0.51 mH 
C)  0.13 mH 
D)  1.0 mH 
E)  8.0 mH

Question 3

If the magnetic flux through a certain region is changing with time:

Accepted Answer

A)  energy must be dissipated as heat 
B)  an electric field must exist at the boundary 
C)  a current must flow around the boundary 
D)  an emf must exist around the boundary 
E)  a magnetic field must exist at the boundary 
A)  energy must be dissipated as heat 
B)  an electric field must exist at the boundary 
C)  a current must flow around the boundary 
D)  an emf must exist around the boundary 
E)  a magnetic field must exist at the boundary

Question 4

1 weber is the same as:

Accepted Answer

A)  1 V/s 
B)  1 T/s 
C)  1 T/m 
D)  1 T.m2 
E)  1 T/m2 
A)  1 V/s 
B)  1 T/s 
C)  1 T/m 
D)  1 T.m2 
E)  1 T/m2

Question 5

The diagram shows an inductor that is part of a circuit. The direction of the emf induced in the inductor is indicated. Which of the following is possible?

Accepted Answer

A)  The current is constant and rightward 
B)  The current is constant and leftward 
C)  The current is increasing and rightward 
D)  The current is increasing and leftward 
E)  None of the above 
A)  The current is constant and rightward 
B)  The current is constant and leftward 
C)  The current is increasing and rightward 
D)  The current is increasing and leftward 
E)  None of the above

Question 6

A vertical bar magnet is dropped through the center of a horizontal loop of wire, with its north pole leading. At the instant when the midpoint of the magnet is in the plane of the loop, the induced current at point P, viewed from above, is:

Accepted Answer

A)  maximum and clockwise 
B)  maximum and counterclockwise 
C)  not maximum but clockwise 
D)  not maximum but counterclockwise 
E)  essentially zero 
A)  maximum and clockwise 
B)  maximum and counterclockwise 
C)  not maximum but clockwise 
D)  not maximum but counterclockwise 
E)  essentially zero

Question 7

1 weber is the same as:

Accepted Answer

A)  1 V . s 
B)  1 T . s 
C)  1 T/m 
D)  1 V/s 
E)  1 T/m2 
A)  1 V . s 
B)  1 T . s 
C)  1 T/m 
D)  1 V/s 
E)  1 T/m2

Question 8

Suppose this page is perpendicular to a uniform magnetic field and the magnetic flux through it is 5 Wb. If the page is turned by 30$\degree$ around an edge the flux through it will be:

Accepted Answer

A)  2.5 Wb 
B)  4.3 Wb 
C)  5 Wb 
D)  5.8 Wb 
E)  10 Wb 
A)  2.5 Wb 
B)  4.3 Wb 
C)  5 Wb 
D)  5.8 Wb 
E)  10 Wb

Question 9

A rod of length L and electrical resistance R moves through a constant uniform magnetic field   perpendicular to the rod. The force that must be applied by a person to keep the rod moving with constant velocity   is:

Accepted Answer

A)  0 
B)  BLv 
C)  BLv/R 
D)  B2L2v/R 
E)  B2L2v2/R 
A)  0 
B)  BLv 
C)  BLv/R 
D)  B2L2v/R 
E)  B2L2v2/R

Question 10

A changing magnetic field pierces the interior of a circuit containing three identical resistors. Two voltmeters are connected to the same points, as shown. V1 reads 1 mV. V2 reads:

Accepted Answer

A)  0 
B)  1/3 mV 
C)  1/2 mV 
D)  1 mV 
E)  2 mV 
A)  0 
B)  1/3 mV 
C)  1/2 mV 
D)  1 mV 
E)  2 mV

Question 11

A magnet moves inside a coil. Consider the following factors:   Which can affect the emf induced in the coil?

Accepted Answer

A)  I only 
B)  II only 
C)  III only 
D)  I and II only 
E)  I, II, III 
A)  I only 
B)  II only 
C)  III only 
D)  I and II only 
E)  I, II, III

Question 12

The diagrams show three circuits with identical batteries, identical inductors, and identical resistors. Rank them according to the current through the battery just after the switch is closed, from least to greatest.

Accepted Answer

A)  3, 2, 1 
B)  2 and 3 ties, then 1 
C)  1, 3, 2 
D)  1, 2, 3 
E)  3, 1, 2 
A)  3, 2, 1 
B)  2 and 3 ties, then 1 
C)  1, 3, 2 
D)  1, 2, 3 
E)  3, 1, 2

Question 13

An inductance L, resistance R, and ideal battery of emf $\varepsilon$ are wired in series. A switch in the circuit is closed at time 0, at which time the current is zero. At any later time t the current i is given by:

Accepted Answer

A)  ($\varepsilon$/R)(1 - e-Lt/R) 
B)  ($\varepsilon$/R)e-Lt/R 
C)  ($\varepsilon$/R)(1 + e-Rt/L) 
D)  ($\varepsilon$/R)e-Rt/L 
E)  ($\varepsilon$/R)(1 - e-Rt/L) 
A)  ($\varepsilon$/R)(1 - e-Lt/R) 
B)  ($\varepsilon$/R)e-Lt/R 
C)  ($\varepsilon$/R)(1 + e-Rt/L) 
D)  ($\varepsilon$/R)e-Rt/L 
E)  ($\varepsilon$/R)(1 - e-Rt/L)

Question 14

A rectangular loop of wire has area A. It is placed perpendicular to a uniform magnetic field B and then spun around one of its sides at frequency f. The maximum induced emf is:

Accepted Answer

A)  BAf 
B)  BA 
C)  2BAf 
D)  2 $\pi$BAf 
E)  4 $\pi$BAf 
A)  BAf 
B)  BA 
C)  2BAf 
D)  2 $\pi$BAf 
E)  4 $\pi$BAf

Question 15

The graph shows the magnitude B of a uniform magnetic field that is perpendicular to the plane of a conducting loop. Rank the five regions indicated on the graph according to the magnitude of the emf induced in the loop, from least to greatest.

Accepted Answer

A)  1, 2, 3, 4 
B)  2, 4, 3, 2 
C)  4, 3, 1, 2 
D)  1, 3, 4, 2 
E)  4, 3, 2, 1 
A)  1, 2, 3, 4 
B)  2, 4, 3, 2 
C)  4, 3, 1, 2 
D)  1, 3, 4, 2 
E)  4, 3, 2, 1

Question 16

An 8.0-mH inductor and a 2.0-(\Omega\)  resistor are wired in series to a 20-V ideal battery. A switch in the circuit is closed at time 0, at which time the current is zero. Immediately after the switch is thrown the potential differences across the inductor and resistor are:

Accepted Answer

A)  0, 20 V 
B)  20 V, 0 
C)  10 V, 10 V 
D)  16 V, 4 V 
E)  unknown since the rate of the current is not given 
A)  0, 20 V 
B)  20 V, 0 
C)  10 V, 10 V 
D)  16 V, 4 V 
E)  unknown since the rate of the current is not given

Question 17

A single loop of wire with a radius of 7.5 cm rotates about a diameter in a uniform magnetic field of 1.6 T. To produce a maximum emf of 1.0 V, it should rotate at:

Accepted Answer

A)  0 
B)  2.7 rad/s 
C)  5.6 rad/s 
D)  35 rad/s 
E)  71 rad/s 
A)  0 
B)  2.7 rad/s 
C)  5.6 rad/s 
D)  35 rad/s 
E)  71 rad/s

Question 18

Immediately after switch S in the circuit shown is closed, the current through the battery is:

Accepted Answer

A)  0 
B)  V0/R1 
C)  V0/R2 
D)  V0/(R1 + R2) 
E)  V0(R1 + R2)/(R1R2) 
A)  0 
B)  V0/R1 
C)  V0/R2 
D)  V0/(R1 + R2) 
E)  V0(R1 + R2)/(R1R2)

Question 19

A 0.20-cm radius cylinder, 3.0 cm long, is wrapped with wire to form an inductor. At the instant the magnetic field in the interior is 5.0 mT the energy stored in the field is:

Accepted Answer

A)  0 
B)  3.8 * 10-6 J 
C)  7.5 * 10-6 J 
D)  7.5 *10-4 J 
E)  9.9 J 
A)  0 
B)  3.8 * 10-6 J 
C)  7.5 * 10-6 J 
D)  7.5 *10-4 J 
E)  9.9 J

Question 20

A circular loop of wire is positioned half in and half out of a square region of constant uniform magnetic field directed into the page, as shown. To induce a clockwise current in this loop:

Accepted Answer

A)  move it in +x direction 
B)  move it in +y direction 
C)  move it in -y direction 
D)  move it in -x direction 
E)  increase the strength of the magnetic field 
A)  move it in +x direction 
B)  move it in +y direction 
C)  move it in -y direction 
D)  move it in -x direction 
E)  increase the strength of the magnetic field

Exam 30: Induction and Inductance

The quantity (B2/ μ\muμ o) has units of:

A 3.5 mH inductor and a 4.5 mH inductor are connected in series. The equivalent inductance is:

If the magnetic flux through a certain region is changing with time:

1 weber is the same as:

The diagram shows an inductor that is part of a circuit. The direction of the emf induced in the inductor is indicated. Which of the following is possible?

A vertical bar magnet is dropped through the center of a horizontal loop of wire, with its north pole leading. At the instant when the midpoint of the magnet is in the plane of the loop, the induced current at point P, viewed from above, is:

1 weber is the same as:

Suppose this page is perpendicular to a uniform magnetic field and the magnetic flux through it is 5 Wb. If the page is turned by 30 °\degree° around an edge the flux through it will be:

A rod of length L and electrical resistance R moves through a constant uniform magnetic field perpendicular to the rod. The force that must be applied by a person to keep the rod moving with constant velocity is:

A changing magnetic field pierces the interior of a circuit containing three identical resistors. Two voltmeters are connected to the same points, as shown. V1 reads 1 mV. V2 reads:

A magnet moves inside a coil. Consider the following factors: Which can affect the emf induced in the coil?

The diagrams show three circuits with identical batteries, identical inductors, and identical resistors. Rank them according to the current through the battery just after the switch is closed, from least to greatest.

An inductance L, resistance R, and ideal battery of emf ε\varepsilonε are wired in series. A switch in the circuit is closed at time 0, at which time the current is zero. At any later time t the current i is given by:

A rectangular loop of wire has area A. It is placed perpendicular to a uniform magnetic field B and then spun around one of its sides at frequency f. The maximum induced emf is:

The graph shows the magnitude B of a uniform magnetic field that is perpendicular to the plane of a conducting loop. Rank the five regions indicated on the graph according to the magnitude of the emf induced in the loop, from least to greatest.

An 8.0-mH inductor and a 2.0-(\Omega\) resistor are wired in series to a 20-V ideal battery. A switch in the circuit is closed at time 0, at which time the current is zero. Immediately after the switch is thrown the potential differences across the inductor and resistor are:

A single loop of wire with a radius of 7.5 cm rotates about a diameter in a uniform magnetic field of 1.6 T. To produce a maximum emf of 1.0 V, it should rotate at:

Immediately after switch S in the circuit shown is closed, the current through the battery is:

A 0.20-cm radius cylinder, 3.0 cm long, is wrapped with wire to form an inductor. At the instant the magnetic field in the interior is 5.0 mT the energy stored in the field is:

A circular loop of wire is positioned half in and half out of a square region of constant uniform magnetic field directed into the page, as shown. To induce a clockwise current in this loop:

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The quantity (B²/ $\mu$ _o) has units of:

Suppose this page is perpendicular to a uniform magnetic field and the magnetic flux through it is 5 Wb. If the page is turned by 30 $\degree$ around an edge the flux through it will be:

A changing magnetic field pierces the interior of a circuit containing three identical resistors. Two voltmeters are connected to the same points, as shown. V₁ reads 1 mV. V₂ reads:

An inductance L, resistance R, and ideal battery of emf $\varepsilon$ are wired in series. A switch in the circuit is closed at time 0, at which time the current is zero. At any later time t the current i is given by: