PHY 131 EXAM 8 | QUESTIONS AND
ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTIONS
Three resistors, each of different value, are used in a circuit with a power source supplying 12 volts. For which of
the following resistor combinations is the total power supplied the greatest? a. all three resistors in series b. all
three resistors in parallel c. two of the resistors in parallel with the third resistor in series with the parallel pair d.
This cannot be found until it is known which resistor is in series with the parallel pair - ANSWER>b
A certain capacitor is charged to 10 V and then, at t = 0, allowed to discharge through a certain resistor. There will
be a certain time before the voltage across the capacitor reaches 5 V. This time can be decreased for this circuit by
increasing: a. the size of the capacitor. b. the size of the resistor. c. the size of the time constant. d. None of the
above. - ANSWER>d
Resistors of values R1 = 6.00 Ω, R2 = 4.00 Ω, R3 = 10.0 Ω, and R4 = 7.00 Ω are combined as shown. What is the
equivalent resistance for this combination? a. 2.30 Ω b. 3.00 Ω c. 10.7 Ω d. 27.0 Ω - ANSWER>c
Which two resistors are in parallel with each other? a. R and R4 b. R2 and R3 c. R2 and R4 d. R and R1 - ANSWER>b
,Two resistors of values 7.0 and 15.0 Ω are connected in parallel. This combination in turn is hooked in series with a
3.0-Ω resistor and a 22.3-V battery. What is the current in the 3.0-Ω resistor? a. 22 A b. 2.9 A c. 0.89 A d. 7.4 A e.
170 A - ANSWER>b
A hair dryer draws 1 400 W, a curling iron draws 850 W, and an electric light fixture draws 600 W. If all three of
these appliances are operating in parallel on a 120-V circuit, what is the total current drawn? a. 7.92 A b. 23.8 A c.
2.34 A d. 30.8 A e. 11.7 A - ANSWER>b
What is the maximum number of 70-W light bulbs you can connect in parallel in a 120-V home circuit without
tripping the 30-A circuit breaker? a. 17 b. 25 c. 51 d. 38 e. 63 - ANSWER>c
A superconducting solenoid is to be designed to generate a magnetic field of 6.20 T. If the solenoid winding has 904
turns/m, what is the required current? (µ0 = 4π × 10−7 T⋅m/A) a. 2.7E+3 A b. 1.7E+3 A c. 5.5E+3 A d. 8.7E+2 A e.
1.4E+2 A - ANSWER>c
. A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron
has the same charge as the proton but has twice its mass. The ratio of the acceleration of the proton to that of the
deuteron is: a. 0.5. b. 1. c. 2. d. There is no acceleration in this case. - ANSWER>c
, Two long parallel wires 44.5 cm apart are carrying currents of 14.3 A and 23.8 A in the same direction. What is the
magnitude of the magnetic field halfway between the wires? a. 8.54E-6 T b. 3.42E-5 T c. 1.29E-5 T d. 2.14E-5 T e.
4.27E-6 T - ANSWER>a
A 114-m-long wire carrying a current of 3.3 A will be accompanied by a magnetic field of what strength at a
distance of 0.026 m from the wire? (magnetic permeability in empty space µ0 = 4π × 10−7 T⋅m/A) a. 8.0E-5 T b.
1.6E-5 T c. 2.5E-5 T d. 1.3E-5 T e. zero - ANSWER>c
Two insulated current-carrying straight wires of equal length are arranged in the lab so that Wire A carries a current
northward and Wire B carries a current eastward, the wires crossing at their midpoints separated only by their
insulation. Which of the following statements are true? a. The net force on Wire B is southward. b. The net force on
Wire A is westward. c. There are no forces in this situation. d. There are forces, but the net force on each wire is
zero - ANSWER>d
A square coil and a triangular coil each have sides of length L. The triangular coil has twice as many turns as the
square coil. If a the same current is sent through each coil, when the coils are placed in the same uniform magnetic
field making an angle of 30° with the planes of the coils, which coil experiences the greater torque? a. the square
coil b. the triangular coil c. Both coils experience the same torque. d. It depends on the magnitude of the magnetic
field that the coils are placed in. - ANSWER>a
ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTIONS
Three resistors, each of different value, are used in a circuit with a power source supplying 12 volts. For which of
the following resistor combinations is the total power supplied the greatest? a. all three resistors in series b. all
three resistors in parallel c. two of the resistors in parallel with the third resistor in series with the parallel pair d.
This cannot be found until it is known which resistor is in series with the parallel pair - ANSWER>b
A certain capacitor is charged to 10 V and then, at t = 0, allowed to discharge through a certain resistor. There will
be a certain time before the voltage across the capacitor reaches 5 V. This time can be decreased for this circuit by
increasing: a. the size of the capacitor. b. the size of the resistor. c. the size of the time constant. d. None of the
above. - ANSWER>d
Resistors of values R1 = 6.00 Ω, R2 = 4.00 Ω, R3 = 10.0 Ω, and R4 = 7.00 Ω are combined as shown. What is the
equivalent resistance for this combination? a. 2.30 Ω b. 3.00 Ω c. 10.7 Ω d. 27.0 Ω - ANSWER>c
Which two resistors are in parallel with each other? a. R and R4 b. R2 and R3 c. R2 and R4 d. R and R1 - ANSWER>b
,Two resistors of values 7.0 and 15.0 Ω are connected in parallel. This combination in turn is hooked in series with a
3.0-Ω resistor and a 22.3-V battery. What is the current in the 3.0-Ω resistor? a. 22 A b. 2.9 A c. 0.89 A d. 7.4 A e.
170 A - ANSWER>b
A hair dryer draws 1 400 W, a curling iron draws 850 W, and an electric light fixture draws 600 W. If all three of
these appliances are operating in parallel on a 120-V circuit, what is the total current drawn? a. 7.92 A b. 23.8 A c.
2.34 A d. 30.8 A e. 11.7 A - ANSWER>b
What is the maximum number of 70-W light bulbs you can connect in parallel in a 120-V home circuit without
tripping the 30-A circuit breaker? a. 17 b. 25 c. 51 d. 38 e. 63 - ANSWER>c
A superconducting solenoid is to be designed to generate a magnetic field of 6.20 T. If the solenoid winding has 904
turns/m, what is the required current? (µ0 = 4π × 10−7 T⋅m/A) a. 2.7E+3 A b. 1.7E+3 A c. 5.5E+3 A d. 8.7E+2 A e.
1.4E+2 A - ANSWER>c
. A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron
has the same charge as the proton but has twice its mass. The ratio of the acceleration of the proton to that of the
deuteron is: a. 0.5. b. 1. c. 2. d. There is no acceleration in this case. - ANSWER>c
, Two long parallel wires 44.5 cm apart are carrying currents of 14.3 A and 23.8 A in the same direction. What is the
magnitude of the magnetic field halfway between the wires? a. 8.54E-6 T b. 3.42E-5 T c. 1.29E-5 T d. 2.14E-5 T e.
4.27E-6 T - ANSWER>a
A 114-m-long wire carrying a current of 3.3 A will be accompanied by a magnetic field of what strength at a
distance of 0.026 m from the wire? (magnetic permeability in empty space µ0 = 4π × 10−7 T⋅m/A) a. 8.0E-5 T b.
1.6E-5 T c. 2.5E-5 T d. 1.3E-5 T e. zero - ANSWER>c
Two insulated current-carrying straight wires of equal length are arranged in the lab so that Wire A carries a current
northward and Wire B carries a current eastward, the wires crossing at their midpoints separated only by their
insulation. Which of the following statements are true? a. The net force on Wire B is southward. b. The net force on
Wire A is westward. c. There are no forces in this situation. d. There are forces, but the net force on each wire is
zero - ANSWER>d
A square coil and a triangular coil each have sides of length L. The triangular coil has twice as many turns as the
square coil. If a the same current is sent through each coil, when the coils are placed in the same uniform magnetic
field making an angle of 30° with the planes of the coils, which coil experiences the greater torque? a. the square
coil b. the triangular coil c. Both coils experience the same torque. d. It depends on the magnitude of the magnetic
field that the coils are placed in. - ANSWER>a
