PHYSICS 131 EXAM 3 QUESTIONS AND ANSWERS
How is the energy stored in a current-carrying inductor related to the current value, I? a.
directly proportional to I 2 b. directly proportional to I 1/2 c. directly proportional to I d.
inversely proportional to I - Answers - a
When a voltage is generated by rotating a coil in a magnetic field at a constant rate, the
period of the voltage equals the time that it takes for the coil to rotate through ________
radians. a. 1 b. π/2 c. π d. 2π - Answers - d
By what factor is the self-inductance of an air solenoid changed if only its cross-
sectional area, A, multiplied by eight? a. 1/8 b. 8 c. 24 d. 64 e. 1/64 - Answers - b
A circular loop is suspended in a uniform magnetic field as shown in the figure
B--> in
If the loop area increases, what affect does this have on the induced current? a. The
induced current is clockwise. b. The induced current is counterclockwise. c. There is no
induced current. d. We would need to know the magnitude of the magnetic field. -
Answers - b
Electricity may be generated by rotating a loop of wire between the poles of a magnet.
The induced current is greatest when a. the plane of the loop is parallel to the magnetic
field. b. the plane of the loop is perpendicular to the magnetic field. c. the magnetic flux
through the loop is a maximum. d. the plane of the loop makes an angle of 45° with the
magnetic field - Answers - a
If the induced current in a wire loop were such that the flux it produces were in the same
direction as the change in external flux causing the current, which of the following
conservation laws would end up being violated? a. momentum b. charge c. energy d.
angular momentum - Answers - c
The operation of an electric motor depends on which of the following effects? a. the
Doppler effect b. the photoelectric effect c. the force acting on a current-carrying wire in
a magnetic field d. current from the motion of a wire in a magnetic field - Answers - c
An inductor, battery, resistance, and ammeter and switch are connected in series. If the
switch, initially open, is now closed, what is the current's final value? a. zero b. battery
voltage divided by inductance c. battery voltage times inductance d. battery voltage
divided by resistance - Answers - d
The units T·m2 /s are equivalent to: a. W. b. V. c. N/m. d. webers. - Answers - b
, The function of the electric motor is which one of the following conversion processes? a.
mechanical energy to electrical b. electrical energy to mechanical c. low voltage to high
or vice versa d. alternating current to direct - Answers - b
The magnet moving past an object will produce eddy currents in the object if the object:
a. is magnetic material only. b. is a conductor. c. is an insulator. d. is a liquid - Answers -
b
A changing current in one loop of wire can induce a current in another loop of wire even
though the wires do not touch. The induced current appears almost instantaneously for
loops close together. How can this energy exchange happen? a. This is one of those
things for which science has no adequate explanation yet. b. The second loop is
affected by the thermal exchange from the heating of the first loop. c. It is a gravitational
effect on the electrons. d. It is done via an electromagnetic wave. - Answers - d
How is the energy stored in a current-carrying inductor related to its self-inductance, L?
a. directly proportional to L2 b. directly proportional to L1/2 c. directly proportional to L d.
inversely proportional to L - Answers - c
A uniform 8.00-T magnetic field passes perpendicularly through the plane of a wire loop
0.320 m2 in area. What flux passes through the loop? a. 25.6 T⋅m2 b. 2.56 T⋅m2 c. 25.0
T⋅m2 d. 0.819 T⋅m2 e. 7.68 T·m2 - Answers - b
A bar magnet is held stationary while a circular loop of wire is moved toward the magnet
at constant velocity at position A as in the figure. The loop passes over the magnet's
center at position B and moves away from the magnet at position C. Viewing the loop
from the left as indicated in the figure, for which position is the induced current zero? a.
Position A b. Position B c. Position C d. The induced current is never zero - Answers - b
The rate of heat dissipation in an AC circuit with resistance, R, and effective current,
Irms, is given by which of the following? a. 0.5 × (Irms) 2 R b. (Irms) 2 R c. 2.0 × (Irms)
2 R d. 4.0 × (Irms) 2 R - Answers - b
Consider an AC series circuit containing a coil, capacitor and resistance. Tripling the
frequency will change the circuit's impedance by what factor? a. 1/3 b. 1.0 c. 3 d.
Information is insufficient to determine answer - Answers - d
Which of the following combinations of circuit components can be used to make a tuner
for a radio, to select the desired frequency? a. fixed inductor, variable resistor b. fixed
resistor, variable inductor c. fixed inductor, variable capacitor d. fixed capacitor, variable
resistor - Answers - c
The peak voltage of an AC source is 296 V. What is the rms voltage? a. 148 V b. 419 V
c. 209 V d. 296 V e. 222 V - Answers - c
How is the energy stored in a current-carrying inductor related to the current value, I? a.
directly proportional to I 2 b. directly proportional to I 1/2 c. directly proportional to I d.
inversely proportional to I - Answers - a
When a voltage is generated by rotating a coil in a magnetic field at a constant rate, the
period of the voltage equals the time that it takes for the coil to rotate through ________
radians. a. 1 b. π/2 c. π d. 2π - Answers - d
By what factor is the self-inductance of an air solenoid changed if only its cross-
sectional area, A, multiplied by eight? a. 1/8 b. 8 c. 24 d. 64 e. 1/64 - Answers - b
A circular loop is suspended in a uniform magnetic field as shown in the figure
B--> in
If the loop area increases, what affect does this have on the induced current? a. The
induced current is clockwise. b. The induced current is counterclockwise. c. There is no
induced current. d. We would need to know the magnitude of the magnetic field. -
Answers - b
Electricity may be generated by rotating a loop of wire between the poles of a magnet.
The induced current is greatest when a. the plane of the loop is parallel to the magnetic
field. b. the plane of the loop is perpendicular to the magnetic field. c. the magnetic flux
through the loop is a maximum. d. the plane of the loop makes an angle of 45° with the
magnetic field - Answers - a
If the induced current in a wire loop were such that the flux it produces were in the same
direction as the change in external flux causing the current, which of the following
conservation laws would end up being violated? a. momentum b. charge c. energy d.
angular momentum - Answers - c
The operation of an electric motor depends on which of the following effects? a. the
Doppler effect b. the photoelectric effect c. the force acting on a current-carrying wire in
a magnetic field d. current from the motion of a wire in a magnetic field - Answers - c
An inductor, battery, resistance, and ammeter and switch are connected in series. If the
switch, initially open, is now closed, what is the current's final value? a. zero b. battery
voltage divided by inductance c. battery voltage times inductance d. battery voltage
divided by resistance - Answers - d
The units T·m2 /s are equivalent to: a. W. b. V. c. N/m. d. webers. - Answers - b
, The function of the electric motor is which one of the following conversion processes? a.
mechanical energy to electrical b. electrical energy to mechanical c. low voltage to high
or vice versa d. alternating current to direct - Answers - b
The magnet moving past an object will produce eddy currents in the object if the object:
a. is magnetic material only. b. is a conductor. c. is an insulator. d. is a liquid - Answers -
b
A changing current in one loop of wire can induce a current in another loop of wire even
though the wires do not touch. The induced current appears almost instantaneously for
loops close together. How can this energy exchange happen? a. This is one of those
things for which science has no adequate explanation yet. b. The second loop is
affected by the thermal exchange from the heating of the first loop. c. It is a gravitational
effect on the electrons. d. It is done via an electromagnetic wave. - Answers - d
How is the energy stored in a current-carrying inductor related to its self-inductance, L?
a. directly proportional to L2 b. directly proportional to L1/2 c. directly proportional to L d.
inversely proportional to L - Answers - c
A uniform 8.00-T magnetic field passes perpendicularly through the plane of a wire loop
0.320 m2 in area. What flux passes through the loop? a. 25.6 T⋅m2 b. 2.56 T⋅m2 c. 25.0
T⋅m2 d. 0.819 T⋅m2 e. 7.68 T·m2 - Answers - b
A bar magnet is held stationary while a circular loop of wire is moved toward the magnet
at constant velocity at position A as in the figure. The loop passes over the magnet's
center at position B and moves away from the magnet at position C. Viewing the loop
from the left as indicated in the figure, for which position is the induced current zero? a.
Position A b. Position B c. Position C d. The induced current is never zero - Answers - b
The rate of heat dissipation in an AC circuit with resistance, R, and effective current,
Irms, is given by which of the following? a. 0.5 × (Irms) 2 R b. (Irms) 2 R c. 2.0 × (Irms)
2 R d. 4.0 × (Irms) 2 R - Answers - b
Consider an AC series circuit containing a coil, capacitor and resistance. Tripling the
frequency will change the circuit's impedance by what factor? a. 1/3 b. 1.0 c. 3 d.
Information is insufficient to determine answer - Answers - d
Which of the following combinations of circuit components can be used to make a tuner
for a radio, to select the desired frequency? a. fixed inductor, variable resistor b. fixed
resistor, variable inductor c. fixed inductor, variable capacitor d. fixed capacitor, variable
resistor - Answers - c
The peak voltage of an AC source is 296 V. What is the rms voltage? a. 148 V b. 419 V
c. 209 V d. 296 V e. 222 V - Answers - c
