Question 1

What is maximum number of 150 W light bulbs that can run on a 130 V (rms) circuit protected by a 20 A (rms) circuit breaker?

Accepted Answer

A)  18 
B)  16 
C)  17 
D)  15 
A)  18 
B)  16 
C)  17 
D)  15

Question 2

A series RLC circuit has a capacitive reactance of 16 Ω and an inductive reactance of 4.0 Ω at 30 Hz. What frequency would result in resonance for this circuit?

Accepted Answer

A)  12 Hz 
B)  60 Hz 
C)  15 Hz 
D)  7.5 Hz 
E)  Resonance is not possible in this case. 
A)  12 Hz 
B)  60 Hz 
C)  15 Hz 
D)  7.5 Hz 
E)  Resonance is not possible in this case.

Question 3

What is the average power for an 8.00 mF capacitor attached to a 120 V rms 60.0 Hz source?

Accepted Answer

A)  240 W 
B)  120 W 
C)  85.0 W 
D)  60.0 W 
E)  0 
A)  240 W 
B)  120 W 
C)  85.0 W 
D)  60.0 W 
E)  0

Question 4

What is the rms current in a 200 mH inductor attached to a 120 V rms, 60.0 Hz source?

Accepted Answer

A)  600 A 
B)  12.0 A 
C)  1.59 A 
D)  100 A 
E)  1.00 A 
A)  600 A 
B)  12.0 A 
C)  1.59 A 
D)  100 A 
E)  1.00 A

Question 5

A series LR circuit dissipates an average power of 60 W. The circuit is powered by a 120 V rms 60 Hz supply. If the current is 2.0 A rms, what is the inductance?

Accepted Answer

A)  0.10 H 
B)  0.15 H 
C)  0.20 H 
D)  0.25 H 
E)  0.30 H 
A)  0.10 H 
B)  0.15 H 
C)  0.20 H 
D)  0.25 H 
E)  0.30 H

Question 6

In an ac circuit, the current in an inductor

Accepted Answer

A)  leads the voltage by 90°. 
B)  lags the voltage by 90°. 
C)  is in phase with the voltage. 
D)  leads the voltage by π radians. 
E)  lags the voltage by π radians. 
A)  leads the voltage by 90°. 
B)  lags the voltage by 90°. 
C)  is in phase with the voltage. 
D)  leads the voltage by π radians. 
E)  lags the voltage by π radians.

Question 7

The current in an RLC circuit when driven at resonance depends on

Accepted Answer

A)  the resonance frequency. 
B)  the resistance. 
C)  the inductive reactance. 
D)  the capacitive reactance. 
E)  More than one of these choices are correct. 
A)  the resonance frequency. 
B)  the resistance. 
C)  the inductive reactance. 
D)  the capacitive reactance. 
E)  More than one of these choices are correct.

Question 8

An ideal diode in an ac circuit

Accepted Answer

A)  doubles the current. 
B)  halves the current. 
C)  permits the current to flow in only one direction. 
D)  permits the current to flow in one direction and double the current to flow in the other. 
E)  permits the current to flow in one direction and half the current to flow in the other. 
A)  doubles the current. 
B)  halves the current. 
C)  permits the current to flow in only one direction. 
D)  permits the current to flow in one direction and double the current to flow in the other. 
E)  permits the current to flow in one direction and half the current to flow in the other.

Question 9

What capacitance is needed in series with a 30 Ω resistor at 1.0 kHz for a total impedance of 45 Ω?

Accepted Answer

A)  34 μF 
B)  15 μF 
C)  4.7 μF 
D)  0.037 μF 
A)  34 μF 
B)  15 μF 
C)  4.7 μF 
D)  0.037 μF

Question 10

A 1500 W hair dryer is run on a 120 V rms circuit. Which of the following is the lowest-rated current breaker that won't open the circuit?

Accepted Answer

A)  10 A 
B)  15 A 
C)  20 A 
D)  30 A 
E)  60 A 
A)  10 A 
B)  15 A 
C)  20 A 
D)  30 A 
E)  60 A

Question 11

What is the resonant frequency of a 1.0 μF capacitor and a 15 mH inductor in series?

Accepted Answer

A)  15 kHz 
B)  1.3 kHz 
C)  0.87 kHz 
D)  57 kHz 
A)  15 kHz 
B)  1.3 kHz 
C)  0.87 kHz 
D)  57 kHz

Question 12

A series RLC ac circuit has a capacitive reactance of 55 Ω, an inductive reactance of 25 Ω, and a resistance of 40 Ω. What is the impedance of this circuit?

Accepted Answer

A)  12 Ω 
B)  95 Ω 
C)  70 Ω 
D)  10 Ω 
E)  50 Ω 
A)  12 Ω 
B)  95 Ω 
C)  70 Ω 
D)  10 Ω 
E)  50 Ω

Question 13

A series RLC circuit has a resistance of 500 Ω, an inductance of 20.0 mH, and a capacitance of 2.00 μF. The source provides a voltage of v(t) = (170 V) sin (377t). What is the peak current in this circuit?

Accepted Answer

A)  92.4 mA 
B)  101 mA 
C)  121 mA 
D)  170 mA 
E)  240 mA 
A)  92.4 mA 
B)  101 mA 
C)  121 mA 
D)  170 mA 
E)  240 mA

Question 14

A series RLC circuit has a resistance of 500 Ω, an inductance of 20.0 mH, and a capacitance of 2.00 μF. The source provides a voltage of v(t) = (170 V) sin (377t). What is the impedance of this circuit?

Accepted Answer

A)  0.402 kΩ 
B)  1.33 kΩ 
C)  1.25 kΩ 
D)  1.41 kΩ 
E)  2.15 kΩ 
A)  0.402 kΩ 
B)  1.33 kΩ 
C)  1.25 kΩ 
D)  1.41 kΩ 
E)  2.15 kΩ

Question 15

For a capacitor in an ac circuit, how much energy is stored in the capacitor at the instant when current is zero?

Accepted Answer

A)  0.707 maximum 
B)  half 
C)  zero 
D)  maximum 
A)  0.707 maximum 
B)  half 
C)  zero 
D)  maximum

Question 16

The capacitive reactance of an RLC circuit is 64 Ω. If the frequency is doubled, what is the new capacitive reactance?

Accepted Answer

A)  18 Ω 
B)  64 Ω 
C)  32 Ω 
D)  8.0 Ω 
E)  4.0 Ω 
A)  18 Ω 
B)  64 Ω 
C)  32 Ω 
D)  8.0 Ω 
E)  4.0 Ω

Question 17

A series RLC circuit has R = 200 Ω, L = 40.0 mH, and C = 120 pF. What is the impedance of this circuit at resonance?

Accepted Answer

A)  18.0 kΩ 
B)  36.0 kΩ 
C)  400 Ω 
D)  300 Ω 
E)  200 Ω 
A)  18.0 kΩ 
B)  36.0 kΩ 
C)  400 Ω 
D)  300 Ω 
E)  200 Ω

Question 18

An RLC series circuit has a 400 Ω resistance, a 2.5 mH inductor, and a capacitor. If the resonant frequency is 30.0 kHz, and the circuit is attached to a 20 mV rms power supply, what is the average power dissipated by the circuit at resonance?

Accepted Answer

A)  1.0 μW 
B)  2.0 μW 
C)  24 mW 
D)  1.2 μW 
E)  1.2 mW 
A)  1.0 μW 
B)  2.0 μW 
C)  24 mW 
D)  1.2 μW 
E)  1.2 mW

Question 19

At what frequency is the reactance of a 20.0 mH inductor equal to 18.8 Ω?

Accepted Answer

A)  75.0 Hz 
B)  150 Hz 
C)  1500 Hz 
D)  15.0 Hz 
A)  75.0 Hz 
B)  150 Hz 
C)  1500 Hz 
D)  15.0 Hz

Question 20

An RLC series circuit has a 400 Ω resistance, a 2.50 mH inductor, and a capacitor. If the resonant frequency is 30.0 kHz, and the circuit is attached to a 20 mV rms power supply, what is the rms current at resonance?

Accepted Answer

A)  60 μA 
B)  40 μA 
C)  30 μA 
D)  50 μA 
E)  25 μA 
A)  60 μA 
B)  40 μA 
C)  30 μA 
D)  50 μA 
E)  25 μA

Exam 21: Alternating Current

What is maximum number of 150 W light bulbs that can run on a 130 V (rms) circuit protected by a 20 A (rms) circuit breaker?

A series RLC circuit has a capacitive reactance of 16 Ω and an inductive reactance of 4.0 Ω at 30 Hz. What frequency would result in resonance for this circuit?

What is the average power for an 8.00 mF capacitor attached to a 120 V rms 60.0 Hz source?

What is the rms current in a 200 mH inductor attached to a 120 V rms, 60.0 Hz source?

A series LR circuit dissipates an average power of 60 W. The circuit is powered by a 120 V rms 60 Hz supply. If the current is 2.0 A rms, what is the inductance?

In an ac circuit, the current in an inductor

The current in an RLC circuit when driven at resonance depends on

An ideal diode in an ac circuit

What capacitance is needed in series with a 30 Ω resistor at 1.0 kHz for a total impedance of 45 Ω?

A 1500 W hair dryer is run on a 120 V rms circuit. Which of the following is the lowest-rated current breaker that won't open the circuit?

What is the resonant frequency of a 1.0 μF capacitor and a 15 mH inductor in series?

A series RLC ac circuit has a capacitive reactance of 55 Ω, an inductive reactance of 25 Ω, and a resistance of 40 Ω. What is the impedance of this circuit?

A series RLC circuit has a resistance of 500 Ω, an inductance of 20.0 mH, and a capacitance of 2.00 μF. The source provides a voltage of v(t) = (170 V) sin (377t). What is the peak current in this circuit?

A series RLC circuit has a resistance of 500 Ω, an inductance of 20.0 mH, and a capacitance of 2.00 μF. The source provides a voltage of v(t) = (170 V) sin (377t). What is the impedance of this circuit?

For a capacitor in an ac circuit, how much energy is stored in the capacitor at the instant when current is zero?

The capacitive reactance of an RLC circuit is 64 Ω. If the frequency is doubled, what is the new capacitive reactance?

A series RLC circuit has R = 200 Ω, L = 40.0 mH, and C = 120 pF. What is the impedance of this circuit at resonance?

An RLC series circuit has a 400 Ω resistance, a 2.5 mH inductor, and a capacitor. If the resonant frequency is 30.0 kHz, and the circuit is attached to a 20 mV rms power supply, what is the average power dissipated by the circuit at resonance?

At what frequency is the reactance of a 20.0 mH inductor equal to 18.8 Ω?

An RLC series circuit has a 400 Ω resistance, a 2.50 mH inductor, and a capacitor. If the resonant frequency is 30.0 kHz, and the circuit is attached to a 20 mV rms power supply, what is the rms current at resonance?

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