Question 1

What is the peak voltage in an ac circuit where the rms voltage is 120 V?

Accepted Answer

A)  84.8 V 
B)  120 V 
C)  170 V 
D)  240 V 
A)  84.8 V 
B)  120 V 
C)  170 V 
D)  240 V

Question 2

A resistor and an inductor are connected in series to a battery. The time constant for the circuit represents the time required for the current to reach

Accepted Answer

A)  25% of the maximum current. 
B)  37% of the maximum current. 
C)  63% of the maximum current. 
D)  75% of the maximum current. 
E)  100% of the maximum current. 
A)  25% of the maximum current. 
B)  37% of the maximum current. 
C)  63% of the maximum current. 
D)  75% of the maximum current. 
E)  100% of the maximum current.

Question 3

In the circuit shown in the figure, the 60-Hz ac source has a voltage amplitude of 120 V, the capacitive reactance is $920 \Omega \text {, }$ the inductive reactance is $290 \Omega$ and the resistance is $420 \Omega$ What is the rms current in the circuit?

Accepted Answer

A)  0.11 A 
B)  0.13 A 
C)  0.14 A 
D)  0.17 A 
E)  0.20 A 
A)  0.11 A 
B)  0.13 A 
C)  0.14 A 
D)  0.17 A 
E)  0.20 A

Question 4

At what frequency will a 20.0-mH inductor have an inductive reactance of 100 Ω?

Accepted Answer

A)  225 Hz 
B)  655 Hz 
C)  796 Hz 
D)  457 Hz 
E)  None of the other answers is correct. 
A)  225 Hz 
B)  655 Hz 
C)  796 Hz 
D)  457 Hz 
E)  None of the other answers is correct.

Question 5

In the circuit shown in the figure, the 60-Hz ac source has a voltage amplitude of 120 V, the capacitive reactance is $820 \Omega$ the inductive reactance is $330 \Omega$ and the resistance is $550 \Omega$ What is the capacitance C of the capacitor?

Accepted Answer

A)  3.2 µF 
B)  6.3 µF 
C)  9.4 µF 
D)  13 µF 
E)  20 µF 
A)  3.2 µF 
B)  6.3 µF 
C)  9.4 µF 
D)  13 µF 
E)  20 µF

Question 6

A series RLC circuit has a 100-Ω resistor, a 0.100-μF capacitor and a 2.00-mH inductor connected across a 120-V rms ac voltage source operating at 1000/π Hz. What is the resonant frequency of this circuit?

Accepted Answer

A)  70.7 kHz 
B)  17.9 kHz 
C)  22.5 kHz 
D)  35.3 kHz 
E)  11.3 kHz 
A)  70.7 kHz 
B)  17.9 kHz 
C)  22.5 kHz 
D)  35.3 kHz 
E)  11.3 kHz

Question 7

The primary coil of an ideal transformer has 600 turns and its secondary coil has 150 turns. If the current in the primary coil is 2 A, what is the current in its secondary coil?

Accepted Answer

A)  8 A 
B)  1/2 A 
C)  1/4 A 
D)  2 A 
E)  4 A 
A)  8 A 
B)  1/2 A 
C)  1/4 A 
D)  2 A 
E)  4 A

Question 8

The primary of an ideal transformer has 100 turns and its secondary has 200 turns. Neglecting frictional losses, if the power input to the primary is 100 W, we can expect the power output of the secondary to be

Accepted Answer

A)  50 W. 
B)  100 W. 
C)  200 W. 
D)  none of the given answers. 
A)  50 W. 
B)  100 W. 
C)  200 W. 
D)  none of the given answers.

Question 9

The figure shows a solenoid having no appreciable resistance. When the current in this solenoid is decreasing at a rate of 5.5 A/s, the self-induced emf in the solenoid is measured to be 9.5 V.
((a) What is the self-inductance of this solenoid?
(b) If the current is in the direction from b to a in the figure, which point, a or b, is at higher potential?

Accepted Answer

(a) 1.7 H

Question 10

In the figure, which of the phasor diagrams represents a series RLC circuit driven at resonance?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5 
A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 11

A 0.150-kW lamp is plugged into a 120-V ac wall outlet. What are (a) the peak current through the lamp, (b) the rms current through the lamp, and (c) the resistance of the lamp?

Accepted Answer

(a) 1.77 A

Question 12

Which of the following statements is true for a series RLC ac circuit in resonance? (There could be more than one correct choice).

Accepted Answer

A)  The inductive reactance and the capacitive reactance are both equal to zero. 
B)  The inductive reactance is equal to the capacitive reactance. 
C)  The current in the circuit is a minimum. 
D)  The current in the circuit is a maximum. 
E)  The rms current is equal to the peak current. 
A)  The inductive reactance and the capacitive reactance are both equal to zero. 
B)  The inductive reactance is equal to the capacitive reactance. 
C)  The current in the circuit is a minimum. 
D)  The current in the circuit is a maximum. 
E)  The rms current is equal to the peak current.

Question 13

A simple circuit consists only of of a 1.0-μF capacitor and a 15-mH coil in series. At what frequency will this circuit oscillate?

Accepted Answer

A)  15 kHz 
B)  1.3 kHz 
C)  0.77 kHz 
D)  67 Hz 
A)  15 kHz 
B)  1.3 kHz 
C)  0.77 kHz 
D)  67 Hz

Question 14

A series circuit contains an 80-μF capacitor, a 0.020-H inductor, and a switch. The resistance of the circuit is negligible. Initially, the switch is open, the capacitor voltage is 50 V, and the current in the inductor is zero. At time t = 0 s, the switch is closed. When the potential across the capacitor is 30 V, what is the rate of change of the current?

Accepted Answer

A)  1000 A/s 
B)  1500 A/s 
C)  2000 A/s 
D)  2500 A/s 
E)  3000 A/s 
A)  1000 A/s 
B)  1500 A/s 
C)  2000 A/s 
D)  2500 A/s 
E)  3000 A/s

Question 15

At what frequency will the capacitive reactance of a 0.010-μF capacitor be 100 Ω?

Accepted Answer

A)  1.0 kHz 
B)  16 kHz 
C)  0.16 MHz 
D)  0.31 MHz 
A)  1.0 kHz 
B)  16 kHz 
C)  0.16 MHz 
D)  0.31 MHz

Question 16

A series circuit has a sinusoidal voltage supplied to it at $632 \mathrm { kHz }$ with a peak voltage of $748 \mathrm {~V}$ It also contains a $\text { 25-k } \Omega$ resistance, a $16 - \mu \mathrm { F }$ capacitance, and a $30 - H$ inductance. What is the peak current for this circuit?

Accepted Answer

A)  6.3 μA 
B)  11 μA 
C)  26 μA 
D)  30 μA 
A)  6.3 μA 
B)  11 μA 
C)  26 μA 
D)  30 μA

Question 17

What is the rms current through a 2.50-mH coil due to a 110-V rms, 60-Hz source?

Accepted Answer

A)  0.94 A 
B)  2.5 A 
C)  104 A 
D)  117 A 
A)  0.94 A 
B)  2.5 A 
C)  104 A 
D)  117 A

Question 18

A 6.0-μF capacitor is connected to an ac signal with a frequency of 60 Hz. If the maximum voltage applied to the capacitor is 8.0 V, what is its capacitive reactance?

Accepted Answer

A)  6.0 Ω 
B)  440 Ω 
C)  7.5 × $10^{ - 6}$ Ω 
D)  740 Ω 
E)  160 Ω 
A)  6.0 Ω 
B)  440 Ω 
C)  7.5 × $10^{ - 6}$ Ω 
D)  740 Ω 
E)  160 Ω

Question 19

A resistance of 55 Ω, a capacitor of capacitive reactance 30 Ω, and an inductor of inductive reactance 30 Ω are connected in series to a 110-V rms 60-Hz power source. What rms current flows in this circuit?

Accepted Answer

A)  more than 4.0 A 
B)  2.0 A 
C)  more than 2.0 A but less than 4.0 A 
D)  4.0 A 
E)  less than 2.0 A 
A)  more than 4.0 A 
B)  2.0 A 
C)  more than 2.0 A but less than 4.0 A 
D)  4.0 A 
E)  less than 2.0 A

Question 20

A 120-V rms voltage at 60 Hz is applied across a series combination of a 20-μF capacitor and an unknown resistor. If the rms value of the current in the circuit is 0.60 A, what is the resistance of the resistor?

Accepted Answer

A)  60 Ω 
B)  120 Ω 
C)  180 Ω 
D)  150 Ω 
E)  200 Ω 
A)  60 Ω 
B)  120 Ω 
C)  180 Ω 
D)  150 Ω 
E)  200 Ω

Exam 26: AC Electricity

What is the peak voltage in an ac circuit where the rms voltage is 120 V?

A resistor and an inductor are connected in series to a battery. The time constant for the circuit represents the time required for the current to reach

In the circuit shown in the figure, the 60-Hz ac source has a voltage amplitude of 120 V, the capacitive reactance is 920Ω, 920 \Omega \text {, }920Ω, the inductive reactance is 290Ω290 \Omega290Ω and the resistance is 420Ω420 \Omega420Ω What is the rms current in the circuit?

At what frequency will a 20.0-mH inductor have an inductive reactance of 100 Ω?

In the circuit shown in the figure, the 60-Hz ac source has a voltage amplitude of 120 V, the capacitive reactance is 820Ω820 \Omega820Ω the inductive reactance is 330Ω330 \Omega330Ω and the resistance is 550Ω550 \Omega550Ω What is the capacitance C of the capacitor?

A series RLC circuit has a 100-Ω resistor, a 0.100-μF capacitor and a 2.00-mH inductor connected across a 120-V rms ac voltage source operating at 1000/π Hz. What is the resonant frequency of this circuit?

The primary coil of an ideal transformer has 600 turns and its secondary coil has 150 turns. If the current in the primary coil is 2 A, what is the current in its secondary coil?

The primary of an ideal transformer has 100 turns and its secondary has 200 turns. Neglecting frictional losses, if the power input to the primary is 100 W, we can expect the power output of the secondary to be

In the figure, which of the phasor diagrams represents a series RLC circuit driven at resonance?

A 0.150-kW lamp is plugged into a 120-V ac wall outlet. What are (a) the peak current through the lamp, (b) the rms current through the lamp, and (c) the resistance of the lamp?

Which of the following statements is true for a series RLC ac circuit in resonance? (There could be more than one correct choice).

A simple circuit consists only of of a 1.0-μF capacitor and a 15-mH coil in series. At what frequency will this circuit oscillate?

At what frequency will the capacitive reactance of a 0.010-μF capacitor be 100 Ω?

What is the rms current through a 2.50-mH coil due to a 110-V rms, 60-Hz source?

A 6.0-μF capacitor is connected to an ac signal with a frequency of 60 Hz. If the maximum voltage applied to the capacitor is 8.0 V, what is its capacitive reactance?

A resistance of 55 Ω, a capacitor of capacitive reactance 30 Ω, and an inductor of inductive reactance 30 Ω are connected in series to a 110-V rms 60-Hz power source. What rms current flows in this circuit?

A 120-V rms voltage at 60 Hz is applied across a series combination of a 20-μF capacitor and an unknown resistor. If the rms value of the current in the circuit is 0.60 A, what is the resistance of the resistor?

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