Question 1

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 2

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

Accepted Answer

A) 0.13 mH 
B) 0.51 mH 
C) 1.0 mH 
D) 2.0 mH 
E) 8.0 mH 
A) 0.13 mH 
B) 0.51 mH 
C) 1.0 mH 
D) 2.0 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 not 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 not 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

When the switch S in the circuit shown is closed, the time constant for the growth of current in R2 is:

Accepted Answer

A) L/R1 
B) L/R2 
C) L/(R1 + R2) 
D) L(R1 + R2)/(R1R2) 
E) (L/R1 + L/R2)/2 
A) L/R1 
B) L/R2 
C) L/(R1 + R2) 
D) L(R1 + R2)/(R1R2) 
E) (L/R1 + L/R2)/2

Question 5

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

Question 6

A uniform magnetic field makes an angle of 30 $\degree$ with the z axis.If the magnetic flux through a 1.0 m2 portion of the xy plane is 5.0 Wb then the magnetic flux through a 2.0 m2 portion of the same plane is:

Accepted Answer

A) 2.5 Wb 
B) 4.3 Wb 
C) 5.0 Wb 
D) 5.8 Wb 
E) 10 Wb 
A) 2.5 Wb 
B) 4.3 Wb 
C) 5.0 Wb 
D) 5.8 Wb 
E) 10 Wb

Question 7

A rectangular loop of wire is placed midway between two long straight parallel conductors as shown.The conductors carry currents i1 and i2 as indicated.If i1 is increasing and i2 is constant, then the induced current in the loop is:

Accepted Answer

A) zero 
B) clockwise 
C) counterclockwise 
D) depends on i1 - i2 
E) depends on i1 + i2 
A) zero 
B) clockwise 
C) counterclockwise 
D) depends on i1 - i2 
E) depends on i1 + i2

Question 8

A long straight wire is in the plane of a rectangular conducting loop.The straight wire initially carries a constant current i in the direction shown.While the current i is being shut off, the current in the loop is:

Accepted Answer

A) zero 
B) clockwise 
C) counterclockwise 
D) clockwise in the left side and counterclockwise in the right side 
E) counterclockwise in the left side and clockwise in the right side 
A) zero 
B) clockwise 
C) counterclockwise 
D) clockwise in the left side and counterclockwise in the right side 
E) counterclockwise in the left side and clockwise in the right side

Question 9

A cylindrical region of radius R = 3.0 cm contains a uniform magnetic field parallel to its axis.If the electric field induced at a point R/2 from the cylinder axis is 4.5 *10-3 V/m the magnitude of the magnetic field must be changing at the rate of:

Accepted Answer

A) 0 T/s 
B) 0.30 T/s 
C) 0.60 T/s 
D) 1.2 T/s 
E) 2.4 T/s 
A) 0 T/s 
B) 0.30 T/s 
C) 0.60 T/s 
D) 1.2 T/s 
E) 2.4 T/s

Question 10

The diagram shows a circular loop of wire that rotates at a steady rate about a diameter O that is perpendicular to a uniform magnetic field.The maximum induced emf occurs when the point X on the loop passes:

Accepted Answer

A) a 
B) b 
C) c 
D) d 
E) e 
A) a 
B) b 
C) c 
D) d 
E) e

Question 11

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

Question 12

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

Accepted Answer

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

Question 13

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

Question 14

One hundred turns of insulated copper wire are wrapped around an iron core of cross-sectional area 0.100 m2.The circuit is completed by connecting the coil to a 10-$\Omega$ resistor.As the magnetic field along the coil axis changes from 1.00 T in one direction to 1.00 T in the other direction, the total charge that flows through the resistor is:

Accepted Answer

A) 0.01 C 
B) 0.02 C 
C) 0.2 C 
D) 1 C 
E) 2 C 
A) 0.01 C 
B) 0.02 C 
C) 0.2 C 
D) 1 C 
E) 2 C

Question 15

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

Question 16

A cylindrical region of radius R contains a uniform magnetic field parallel to its axis.The field is zero outside the cylinder.If the magnitude of the field is changing at the rate dB/dt, the electric field induced at a point 2R from the cylinder axis is:

Accepted Answer

A) 0 
B) 2R dB/dt 
C) R dB/dt 
D) (R/2)dB/dt 
E) (R/4)dB/dt 
A) 0 
B) 2R dB/dt 
C) R dB/dt 
D) (R/2)dB/dt 
E) (R/4)dB/dt

Question 17

An inductor with inductance L and a resistor with resistance R are wired in series to an ideal battery with emf .A switch in the circuit is closed at time t = 0, at which time the current is zero.A long time after the switch is thrown the potential differences across the inductor and resistor are:

Accepted Answer

A) 0, 
B) , 0 
C) /2, /2 
D) (L/R), (R/L) 
E) unknown since the rate of change of the current is not given 
A) 0, 
B) , 0 
C) /2, /2 
D) (L/R), (R/L) 
E) unknown since the rate of change of the current is not given

Question 18

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

Question 19

The magnetic flux ΦB through a surface:

Accepted Answer

A) is the amount of magnetic field piercing the surface. 
B) is the magnetic field multiplied by the area. 
C) does not depend on the area involved. 
D) is the line integral of the magnetic field around the edge of the surface. 
E) is the amount of magnetic field skimming along the surface. 
A) is the amount of magnetic field piercing the surface. 
B) is the magnetic field multiplied by the area. 
C) does not depend on the area involved. 
D) is the line integral of the magnetic field around the edge of the surface. 
E) is the amount of magnetic field skimming along the surface.

Question 20

A square loop of wire moves with a constant speed v from a field-free region into a region of uniform B field, as shown.Which of the five graphs correctly shows the induced current i in the loop as a function of time t?

Accepted Answer

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

Exam 30: Induction and Inductance

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

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

When the switch S in the circuit shown is closed, the time constant for the growth of current in R2 is:

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.

A uniform magnetic field makes an angle of 30 °\degree° with the z axis.If the magnetic flux through a 1.0 m2 portion of the xy plane is 5.0 Wb then the magnetic flux through a 2.0 m2 portion of the same plane is:

A rectangular loop of wire is placed midway between two long straight parallel conductors as shown.The conductors carry currents i1 and i2 as indicated.If i1 is increasing and i2 is constant, then the induced current in the loop is:

A long straight wire is in the plane of a rectangular conducting loop.The straight wire initially carries a constant current i in the direction shown.While the current i is being shut off, the current in the loop is:

A cylindrical region of radius R = 3.0 cm contains a uniform magnetic field parallel to its axis.If the electric field induced at a point R/2 from the cylinder axis is 4.5 *10-3 V/m the magnitude of the magnetic field must be changing at the rate of:

The diagram shows a circular loop of wire that rotates at a steady rate about a diameter O that is perpendicular to a uniform magnetic field.The maximum induced emf occurs when the point X on the loop passes:

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?

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

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 between the rails should be in what direction?

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:

A cylindrical region of radius R contains a uniform magnetic field parallel to its axis.The field is zero outside the cylinder.If the magnitude of the field is changing at the rate dB/dt, the electric field induced at a point 2R from the cylinder axis is:

An inductor with inductance L and a resistor with resistance R are wired in series to an ideal battery with emf .A switch in the circuit is closed at time t = 0, at which time the current is zero.A long time after the switch is thrown the potential differences across the inductor and resistor are:

The unit "henry" is equivalent to:

The magnetic flux ΦB through a surface:

A square loop of wire moves with a constant speed v from a field-free region into a region of uniform B field, as shown.Which of the five graphs correctly shows the induced current i in the loop as a function of time t?

Measurement

Motion Along a Straight Line

Vector

Motion in Two and Three Dimensions

Force and Motion I

Force and Motion II

Kinetic Energy and Work

Potential Energy and Conservation of Energy

Center of Mass and Linear Momentum

Rotation

Rolling, Torque, and Angular Momentum

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The Kinetic Theory of Gases

Entropy and the Second Law of Thermodynamics

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Relativity

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Energy From the Nucleus

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Filters

When the switch S in the circuit shown is closed, the time constant for the growth of current in R₂ is:

A uniform magnetic field makes an angle of 30 $\degree$ with the z axis.If the magnetic flux through a 1.0 m² portion of the xy plane is 5.0 Wb then the magnetic flux through a 2.0 m² portion of the same plane is:

A rectangular loop of wire is placed midway between two long straight parallel conductors as shown.The conductors carry currents i₁ and i₂ as indicated.If i₁ is increasing and i₂ is constant, then the induced current in the loop is:

A cylindrical region of radius R = 3.0 cm contains a uniform magnetic field parallel to its axis.If the electric field induced at a point R/2 from the cylinder axis is 4.5 *10^-3 V/m the magnitude of the magnetic field must be changing at the rate of:

The magnetic flux Φ_B through a surface: