Question 1

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

Question 2

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

Question 3

The units of motional emf are:

Accepted Answer

A)   volt/second
B)   volt.meter/second
C)   volt/tesla
D)   tesla/second
E)   tesla.meter2/second

Question 4

As an externally generated magnetic field through a certain conducting loop increases in magnitude, the field produced at points inside the loop by the current induced in the loop must be:

Accepted Answer

A)   increasing in magnitude
B)   decreasing in magnitude
C)   in the same direction as the applied field
D)   directed opposite to the applied field
E)   perpendicular to the applied field

Question 5

The normal to a certain 1-m2 area makes an angle of 60  °\degree°  with a uniform magnetic field. The magnetic flux through this area is the same as the flux through a second area that is perpendicular to the field if the second area is:

Accepted Answer

A)   0.866 m2
B)   1.15 m2
C)   0.5 m2
D)   2 m2
E)   1 m2

Question 6

The unit "henry" is equivalent to:

Accepted Answer

A)   volt.second/ampere
B)   volt/second
C)   ohm
D)   ampere.volt/second
E)   ampere.second/volt

Question 7

The four wire loops shown have edge lengths of either L, 2L, or 3L. They will move with the same speed into a region of uniform magnetic field  directed out of the page. Rank them according to the maximum magnitude of the induced emf, least to greatest.

Accepted Answer

A)   1 and 2 tie, then 3 and 4 tie
B)   3 and 4 tie, then 1 and 2 tie
C)   4, 2, 3, 1
D)   1, then 2 and 3 tie, then 4
E)   1, 2, 3, 4

Question 8

The figure shows a bar moving to the right on two conducting rails. To make an induced current i in the direction indicated, a constant magnetic field in region A should be in what direction?

Accepted Answer

A)   Right
B)   Left
C)   Into the page
D)   Out of the page
E)   Impossible, cannot be done with a constant magnetic field

Question 9

An 8.0-mH inductor and a 2.0- Ω\OmegaΩ  resistor are wired in series to an ideal battery. A switch in the circuit is closed at time 0, at which time the current is 0. The current reaches half its final value at a time of:

Accepted Answer

A)   2.8 ms
B)   4.0 ms
C)   3 s
D)   170 s
E)   250 s

Question 10

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

Question 11

A 3.5 mH inductor and a 4.5 mH inductor are connected in series and a time varying current is established in them. When the total emf of the combination is 16 V, the emf of the larger inductor is:

Accepted Answer

A)   7.0 V
B)   9.0 V
C)   2.3 V
D)   28 V
E)   36 V

Question 12

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

Question 13

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

Accepted Answer

A)   the flux is zero
B)   the flux is a maximum
C)   the flux is half its maximum value
D)   the derivative of the flux with respect to time is zero
E)   none of the above

Question 14

A copper penny slides on a horizontal frictionless table. There is a square region of constant uniform magnetic field perpendicular to the table, as shown. Which graph correctly shows the speed v of the penny as a function of time t?

Accepted Answer

A)   I
B)   II
C)   III
D)   IV
E)   V

Question 15

You push a permanent magnet with its north pole away from you toward a loop of conducting wire in front of you. Before the north pole enters the loop the current in the loop is:

Accepted Answer

A)   zero
B)   clockwise
C)   counterclockwise
D)   to your left
E)   to your right

Question 16

A circular loop of wire rotates about a diameter in a magnetic field that is perpendicular to the axis of rotation. Looking in the direction of the field at the loop the induced current is:

Accepted Answer

A)   always clockwise
B)   always counterclockwise
C)   clockwise in the lower half of the loop and counterclockwise in the upper half
D)   clockwise in the upper half of the loop and counterclockwise in the lower half
E)   sometimes clockwise and sometimes counterclockwise

Question 17

A car travels northward at 75 km/h along a straight road in a region where Earth's magnetic field has a vertical component of 0.50 *10-4 T. The emf induced between the left and right side, separated by 1.7 m, is:

Accepted Answer

A)   0
B)   1.8 mV
C)   3.6 mV
D)   6.4 mV
E)   13 mV

Question 18

A square loop of wire lies in the plane of the page. A decreasing magnetic field is directed into the page. The induced current in the loop is:

Accepted Answer

A)   counterclockwise
B)   clockwise
C)   zero
D)   up the left edge and from right to left alongthe top edge
E)   throught the middle of the page

Question 19

An 8.0-mH inductor and a 2.0- Ω\OmegaΩ  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. After a long time the current in the resistor and the current in the inductor are:

Accepted Answer

A)   0, 0
B)   10 A, 10 A
C)   2.5 A, 2.5 A
D)   10 A, 2.5 A
E)   10 A, 0

Question 20

A cylindrical region of radius R contains a uniform magnetic field, parallel to its axis, with magnitude that is changing linearly with time. If r is the radial distance from the cylinder axis, the magnitude of the induced electric field outside the cylinder is proportional to:

Accepted Answer

A)   R
B)   r
C)   r2
D)   1/r
E)   1/r2

Exam 30: Induction and Inductance

The units of motional emf are:

Correct AnswerverifiedShow Answer

A 3.5 mH inductor and a 4.5 mH inductor are connected in series and a time varying current is established in them. When the total emf of the combination is 16 V, the emf of the larger inductor is:

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A cylindrical region of radius R contains a uniform magnetic field, parallel to its axis, with magnitude that is changing linearly with time. If r is the radial distance from the cylinder axis, the magnitude of the induced electric field outside the cylinder is proportional to:

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The figure shows a bar moving to the right on two conducting rails. To make an induced current i in the direction indicated, a constant magnetic field in region A should be in what direction?

Correct AnswerverifiedShow Answer

As an externally generated magnetic field through a certain conducting loop increases in magnitude, the field produced at points inside the loop by the current induced in the loop must be:

Correct AnswerverifiedShow Answer

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

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An 8.0-mH inductor and a 2.0- Ω\OmegaΩ resistor are wired in series to an ideal battery. A switch in the circuit is closed at time 0, at which time the current is 0. The current reaches half its final value at a time of:

Correct AnswerverifiedShow Answer

The four wire loops shown have edge lengths of either L, 2L, or 3L. They will move with the same speed into a region of uniform magnetic field directed out of the page. Rank them according to the maximum magnitude of the induced emf, least to greatest.

Correct AnswerverifiedShow Answer

A square loop of wire lies in the plane of the page. A decreasing magnetic field is directed into the page. The induced current in the loop is:

Correct AnswerverifiedShow Answer

An 8.0-mH inductor and a 2.0- Ω\OmegaΩ 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. After a long time the current in the resistor and the current in the inductor are:

Correct AnswerverifiedShow Answer

The normal to a certain 1-m2 area makes an angle of 60 °\degree° with a uniform magnetic field. The magnetic flux through this area is the same as the flux through a second area that is perpendicular to the field if the second area is:

Correct AnswerverifiedShow Answer

A circular loop of wire rotates about a diameter in a magnetic field that is perpendicular to the axis of rotation. Looking in the direction of the field at the loop the induced current is:

Correct AnswerverifiedShow Answer

You push a permanent magnet with its north pole away from you toward a loop of conducting wire in front of you. Before the north pole enters the loop the current in the loop is:

Correct AnswerverifiedShow Answer

A copper penny slides on a horizontal frictionless table. There is a square region of constant uniform magnetic field perpendicular to the table, as shown. Which graph correctly shows the speed v of the penny as a function of time t?

Correct AnswerverifiedShow Answer

The unit "henry" is equivalent to:

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

A car travels northward at 75 km/h along a straight road in a region where Earth's magnetic field has a vertical component of 0.50 *10-4 T. The emf induced between the left and right side, separated by 1.7 m, is:

Correct AnswerverifiedShow Answer

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:

Correct AnswerverifiedShow Answer

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:

Correct AnswerverifiedShow Answer

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:

Correct AnswerverifiedShow Answer

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

An 8.0-mH inductor and a 2.0- $\Omega$ resistor are wired in series to an ideal battery. A switch in the circuit is closed at time 0, at which time the current is 0. The current reaches half its final value at a time of:

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

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. After a long time the current in the resistor and the current in the inductor are:

Correct Answer
verified

The normal to a certain 1-m² area makes an angle of 60 $\degree$ with a uniform magnetic field. The magnetic flux through this area is the same as the flux through a second area that is perpendicular to the field if the second area is:

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

A car travels northward at 75 km/h along a straight road in a region where Earth's magnetic field has a vertical component of 0.50 *10^-⁴ T. The emf induced between the left and right side, separated by 1.7 m, is:

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

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:

Correct Answer
verified