Question 1

The inductive reactance of a 20-mH inductor at a certain frequency is 120 Ω. What is the frequency in rad/s?

Accepted Answer

A)  2000 rad/s 
B)  4000 rad/s 
C)  5000 rad/s 
D)  6000 rad/s 
E)  7000 rad/s 
A)  2000 rad/s 
B)  4000 rad/s 
C)  5000 rad/s 
D)  6000 rad/s 
E)  7000 rad/s

Question 2

A 50.0-mH inductor is connected in series with a 2500-Ω resistor. What is the phase angle at 3000 Hz?

Accepted Answer

A)  20.7° 
B)  - 20.7° 
C)  -75.9° 
D)  75.9° 
E)  90.0° 
A)  20.7° 
B)  - 20.7° 
C)  -75.9° 
D)  75.9° 
E)  90.0°

Question 3

In a pure resistive circuit, the phase angle between current and voltage is

Accepted Answer

A)  0. 
B)  π/2 radians. 
C)  -π/2 radians. 
D)  π radians. 
E)  3π/4 radians. 
A)  0. 
B)  π/2 radians. 
C)  -π/2 radians. 
D)  π radians. 
E)  3π/4 radians.

Question 4

FIGURE 24-1  
-Figure 24-1 shows a simple ac circuit composed of a capacitor connected across the terminals of an ac generator. If the frequency of the generator is doubled, what happens to the capacitive reactance of the capacitor?

Accepted Answer

A)  It increases by a factor of 4. 
B)  It increases by a factor of 2. 
C)  It increases by a factor of   . 
D)  It decreases by a factor of 2. 
E)  It decreases by a factor of 4. 
A)  It increases by a factor of 4. 
B)  It increases by a factor of 2. 
C)  It increases by a factor of   . 
D)  It decreases by a factor of 2. 
E)  It decreases by a factor of 4.

Question 5

In a RLC circuit, the values of the inductance and capacitance are both halved. In comparison with the resonance frequency of the original circuit, the new resonant frequency will be

Accepted Answer

A)  the same as before. 
B)  reduced to one-half the original value. 
C)  reduced to one-quarter the original value. 
D)  increased by a factor of two. 
E)  increased by a factor of four. 
A)  the same as before. 
B)  reduced to one-half the original value. 
C)  reduced to one-quarter the original value. 
D)  increased by a factor of two. 
E)  increased by a factor of four.

Question 6

A 120-V rms signal at 60.0 Hz is applied across a 30.0-mH inductor and a 100-Ω resistor. What is the rms value of the voltage across the inductor?

Accepted Answer

A)  0.700 V 
B)  119 V 
C)  100 V 
D)  13.5 V 
E)  120 V 
A)  0.700 V 
B)  119 V 
C)  100 V 
D)  13.5 V 
E)  120 V

Question 7

A pure capacitor is connected to an AC power supply. In this circuit, the current

Accepted Answer

A)  leads the voltage by 90°. 
B)  lags the voltage by 90°. 
C)  lags the voltage by 180°. 
D)  is in phase with the voltage. 
E)  none of the given answers 
A)  leads the voltage by 90°. 
B)  lags the voltage by 90°. 
C)  lags the voltage by 180°. 
D)  is in phase with the voltage. 
E)  none of the given answers

Question 8

The circuit power factor of an RL circuit connected across an ac source is one. What would be a good description of the frequency of this source?

Accepted Answer

A)  Low 
B)  Very low 
C)  High 
D)  Very high 
A)  Low 
B)  Very low 
C)  High 
D)  Very high

Question 9

A 200-Ω resistor, 40.0-mH inductor and a 2.00-μF capacitor are connected in series with a 120-V rms source at 1000 Hz. What is the phase angle of this circuit?

Accepted Answer

A)  49.3° 
B)  90.0° 
C)  40.7° 
D)  0° 
E)  45.0° 
A)  49.3° 
B)  90.0° 
C)  40.7° 
D)  0° 
E)  45.0°

Question 10

At what frequency will a 20.00-mH inductor have an inductive reactance of 100.0 Ω?

Accepted Answer

A)  225.4 Hz 
B)  654 .8 Hz 
C)  795.7 Hz 
D)  457.4 Hz 
E)  None of the other answers is correct. 
A)  225.4 Hz 
B)  654 .8 Hz 
C)  795.7 Hz 
D)  457.4 Hz 
E)  None of the other answers is correct.

Question 11

A pure inductor is connected to an AC power supply. In this circuit, the current

Accepted Answer

A)  leads the voltage by 90°. 
B)  is in phase with the voltage. 
C)  lags the voltage by 45°. 
D)  lags the voltage by 90°. 
E)  leads the voltage by 45°. 
A)  leads the voltage by 90°. 
B)  is in phase with the voltage. 
C)  lags the voltage by 45°. 
D)  lags the voltage by 90°. 
E)  leads the voltage by 45°.

Question 12

The capacitive reactance of a 44-μF capacitor in an ac circuit is 6.0 × 102 Ω. What is the frequency of the applied signal?

Accepted Answer

A)  80 Hz 
B)  17 Hz 
C)  800 Hz 
D)  6.0 Hz 
E)  2.2 Hz 
A)  80 Hz 
B)  17 Hz 
C)  800 Hz 
D)  6.0 Hz 
E)  2.2 Hz

Question 13

A 120-V rms voltage is applied across a 6.0-μF capacitor. If the frequency of the generator is 60 Hz, what is the rms value of the current in the circuit?

Accepted Answer

A)  0.47 A 
B)  0.37 A 
C)  0.071 A 
D)  0.17 A 
E)  0.27 A 
A)  0.47 A 
B)  0.37 A 
C)  0.071 A 
D)  0.17 A 
E)  0.27 A

Question 14

A resistor is connected to an AC power supply. On this circuit, the current

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 45°. 
E)  lags the voltage by 45°. 
A)  leads the voltage by 90°. 
B)  lags the voltage by 90°. 
C)  is in phase with the voltage. 
D)  leads the voltage by 45°. 
E)  lags the voltage by 45°.

Question 15

FIGURE 24-2  
-Figure 24-2 shows a simple ac circuit consisting of an inductor connected across the terminals of an ac generator. If the frequency of the ac generator is decreased by a factor of four, what will happen to the inductive reactance on the inductor?

Accepted Answer

A)  It decreases by a factor of four. 
B)  It decreases by a factor of eight. 
C)  It increases by a factor of two. 
D)  It increases by a factor of four. 
E)  It increases by a factor of eight. 
A)  It decreases by a factor of four. 
B)  It decreases by a factor of eight. 
C)  It increases by a factor of two. 
D)  It increases by a factor of four. 
E)  It increases by a factor of eight.

Question 16

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

Question 17

The inductive reactance of a 20.0-mH inductor at a certain frequency is 120 Ω. What is the frequency in Hz?

Accepted Answer

A)  120 Hz 
B)  167 Hz 
C)  478 Hz 
D)  6000 Hz 
E)  955 Hz 
A)  120 Hz 
B)  167 Hz 
C)  478 Hz 
D)  6000 Hz 
E)  955 Hz

Question 18

The phase angle in a series RL circuit at 1000 Hz with a 200-Ω resistor and a certain inductor is 40.0°. What is the value of the inductance in this circuit?

Accepted Answer

A)  83.9 mH 
B)  73.9 mH 
C)  26.7 mH 
D)  36.7 mH 
E)  57.9 mH 
A)  83.9 mH 
B)  73.9 mH 
C)  26.7 mH 
D)  36.7 mH 
E)  57.9 mH

Question 19

A series RLC circuit has a 150-Ω resistor, a 6.00-mH inductor and a 0.200-μF capacitor connected across a 120-V rms ac source at 15.0 kHz. What is the phase angle of the circuit?

Accepted Answer

A)  47.3° 
B)  0° 
C)  45.0° 
D)  90.0° 
E)  73.7° 
A)  47.3° 
B)  0° 
C)  45.0° 
D)  90.0° 
E)  73.7°

Question 20

In a RLC circuit, a second capacitor is connected in parallel with the capacitor previously in the circuit. What is the effect of this change on the impedance of the circuit?

Accepted Answer

A)  It increases. 
B)  It decreases. 
C)  It does not change. 
D)  It increases for frequencies below resonance and decreases for frequencies above resonance. 
E)  It decreases for frequencies below resonance and increases for frequencies above resonance. 
A)  It increases. 
B)  It decreases. 
C)  It does not change. 
D)  It increases for frequencies below resonance and decreases for frequencies above resonance. 
E)  It decreases for frequencies below resonance and increases for frequencies above resonance.

Exam 24: Alternating-Current Circuits

The inductive reactance of a 20-mH inductor at a certain frequency is 120 Ω. What is the frequency in rad/s?

A 50.0-mH inductor is connected in series with a 2500-Ω resistor. What is the phase angle at 3000 Hz?

In a pure resistive circuit, the phase angle between current and voltage is

FIGURE 24-1 -Figure 24-1 shows a simple ac circuit composed of a capacitor connected across the terminals of an ac generator. If the frequency of the generator is doubled, what happens to the capacitive reactance of the capacitor?

In a RLC circuit, the values of the inductance and capacitance are both halved. In comparison with the resonance frequency of the original circuit, the new resonant frequency will be

A 120-V rms signal at 60.0 Hz is applied across a 30.0-mH inductor and a 100-Ω resistor. What is the rms value of the voltage across the inductor?

A pure capacitor is connected to an AC power supply. In this circuit, the current

The circuit power factor of an RL circuit connected across an ac source is one. What would be a good description of the frequency of this source?

A 200-Ω resistor, 40.0-mH inductor and a 2.00-μF capacitor are connected in series with a 120-V rms source at 1000 Hz. What is the phase angle of this circuit?

At what frequency will a 20.00-mH inductor have an inductive reactance of 100.0 Ω?

A pure inductor is connected to an AC power supply. In this circuit, the current

The capacitive reactance of a 44-μF capacitor in an ac circuit is 6.0 × 102 Ω. What is the frequency of the applied signal?

A 120-V rms voltage is applied across a 6.0-μF capacitor. If the frequency of the generator is 60 Hz, what is the rms value of the current in the circuit?

A resistor is connected to an AC power supply. On this circuit, the current

FIGURE 24-2 -Figure 24-2 shows a simple ac circuit consisting of an inductor connected across the terminals of an ac generator. If the frequency of the ac generator is decreased by a factor of four, what will happen to the inductive reactance on the inductor?

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

The inductive reactance of a 20.0-mH inductor at a certain frequency is 120 Ω. What is the frequency in Hz?

The phase angle in a series RL circuit at 1000 Hz with a 200-Ω resistor and a certain inductor is 40.0°. What is the value of the inductance in this circuit?

A series RLC circuit has a 150-Ω resistor, a 6.00-mH inductor and a 0.200-μF capacitor connected across a 120-V rms ac source at 15.0 kHz. What is the phase angle of the circuit?

In a RLC circuit, a second capacitor is connected in parallel with the capacitor previously in the circuit. What is the effect of this change on the impedance of the circuit?

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The capacitive reactance of a 44-μF capacitor in an ac circuit is 6.0 × 10² Ω. What is the frequency of the applied signal?