PHY 131 EXAM 9 | QUESTIONS AND
ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTIONS
To find the equivalent resistance of the combination of resistors shown below by the method of possibly repeated
applications of combining resistors in series and /or combining resistors in parallel, the first step would be which of
the following?
a. Combine the 6.0 Ω and the 7.0 Ω in series.
b. Combine either the 4.0 Ω and the 10.0 Ω in parallel or the 7.0 Ω and the 10.0 Ω in parallel first, since either could
be the first step with the other the second step.
c. Combine the 4.0 Ω and the 10.0 Ω in series.
d. Combine the 6.0 Ω, the 4.0 Ω, and the 10.0 Ω in series in a single step. - ANSWER>Combine the 4.0 Ω and the
10.0 Ω in series.
Three resistors connected in parallel have the individual voltages labeled ΔV1, ΔV2 and ΔV3, respectively. Which of
the following expresses the total voltage ΔVT across the three resistors when connected in this manner?
a. ΔVT = ΔV1 + ΔV2 + ΔV3
b. ΔVT = (1/ΔV1 + 1/ΔV2 + 1/ΔV3)
,c. ΔVT = ΔV1 = ΔV2 = ΔV3
d. ΔVT = (1/ΔV1 + 1/ΔV2 + 1/ΔV3) −1 - ANSWER>ΔVT = ΔV1 = ΔV2 = ΔV3
If I1 goes to the right through R1, I2 goes to the right through R2, and I3 goes to the right through R3, what is the
resulting equation resulting from applying Kirchhoff's junction rule at point b?
a. I1 + I2 + I3 = 0
b. I1 + I2 - I3 = 0
c. I1 - I2 + I3 = 0
d. I1 - I2 - I3 = 0 - ANSWER>I1 + I2 + I3 = 0
Three resistors with values of R1, R2 and R3, respectively, are connected in series. Which of the following expresses
the total resistance, RT, of the three resistors?
a. RT = R1 + R2 + R3
b. RT = (1/R1 + 1/R2 + 1/R3)
c. RT = R1 = R2 = R3
d. RT = (1/R1 + 1/R2 + 1/R3) −1 - ANSWER>RT = R1 + R2 + R3
, When a light bulb is turned on, its resistance increases until it reaches operating temperature. What happens to the
current in the bulb as it is warming up?
a. It stays constant.
b. It increases.
c. It decreases.
d. It increases at first and then decreases - ANSWER>It decreases.
A current in a solenoid with N turns creates a magnetic field at the center of that loop. The field strength is directly
proportional to:
a. number of turns in the loop.
b. current strength.
c. Both choices A and B are valid. d. None of the above are valid. - ANSWER>Both choices A and B are valid.
If a proton is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force
on the proton will be toward the:
a. north.
b. south.
c. east.
ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTIONS
To find the equivalent resistance of the combination of resistors shown below by the method of possibly repeated
applications of combining resistors in series and /or combining resistors in parallel, the first step would be which of
the following?
a. Combine the 6.0 Ω and the 7.0 Ω in series.
b. Combine either the 4.0 Ω and the 10.0 Ω in parallel or the 7.0 Ω and the 10.0 Ω in parallel first, since either could
be the first step with the other the second step.
c. Combine the 4.0 Ω and the 10.0 Ω in series.
d. Combine the 6.0 Ω, the 4.0 Ω, and the 10.0 Ω in series in a single step. - ANSWER>Combine the 4.0 Ω and the
10.0 Ω in series.
Three resistors connected in parallel have the individual voltages labeled ΔV1, ΔV2 and ΔV3, respectively. Which of
the following expresses the total voltage ΔVT across the three resistors when connected in this manner?
a. ΔVT = ΔV1 + ΔV2 + ΔV3
b. ΔVT = (1/ΔV1 + 1/ΔV2 + 1/ΔV3)
,c. ΔVT = ΔV1 = ΔV2 = ΔV3
d. ΔVT = (1/ΔV1 + 1/ΔV2 + 1/ΔV3) −1 - ANSWER>ΔVT = ΔV1 = ΔV2 = ΔV3
If I1 goes to the right through R1, I2 goes to the right through R2, and I3 goes to the right through R3, what is the
resulting equation resulting from applying Kirchhoff's junction rule at point b?
a. I1 + I2 + I3 = 0
b. I1 + I2 - I3 = 0
c. I1 - I2 + I3 = 0
d. I1 - I2 - I3 = 0 - ANSWER>I1 + I2 + I3 = 0
Three resistors with values of R1, R2 and R3, respectively, are connected in series. Which of the following expresses
the total resistance, RT, of the three resistors?
a. RT = R1 + R2 + R3
b. RT = (1/R1 + 1/R2 + 1/R3)
c. RT = R1 = R2 = R3
d. RT = (1/R1 + 1/R2 + 1/R3) −1 - ANSWER>RT = R1 + R2 + R3
, When a light bulb is turned on, its resistance increases until it reaches operating temperature. What happens to the
current in the bulb as it is warming up?
a. It stays constant.
b. It increases.
c. It decreases.
d. It increases at first and then decreases - ANSWER>It decreases.
A current in a solenoid with N turns creates a magnetic field at the center of that loop. The field strength is directly
proportional to:
a. number of turns in the loop.
b. current strength.
c. Both choices A and B are valid. d. None of the above are valid. - ANSWER>Both choices A and B are valid.
If a proton is released at the equator and falls toward the Earth under the influence of gravity, the magnetic force
on the proton will be toward the:
a. north.
b. south.
c. east.
