Question 1

What inductance is needed in series with a 4.7 μF capacitor for a resonant frequency of 10 kHz?

Accepted Answer

A)  22 μH 
B)  54 μH 
C)  0.66 μH 
D)  5.3 mH 
A)  22 μH 
B)  54 μH 
C)  0.66 μH 
D)  5.3 mH

Question 2

An ac circuit has a resistance of 120 Ω and an impedance of 200 Ω. What is the power factor for this circuit?

Accepted Answer

A)  53° 
B)  32° 
C)  0.60 
D)  1.7 
E)  1.3 
A)  53° 
B)  32° 
C)  0.60 
D)  1.7 
E)  1.3

Question 3

The voltage supplied to an ac circuit is given by v(t) = (120 V) sin (60t). What are the rms voltage and the frequency?

Accepted Answer

A)  120 V, 60 Hz 
B)  120 V, 380 Hz 
C)  170 V, 9.5 Hz 
D)  85 V, 9.5 Hz 
E)  240 V, 30 Hz 
A)  120 V, 60 Hz 
B)  120 V, 380 Hz 
C)  170 V, 9.5 Hz 
D)  85 V, 9.5 Hz 
E)  240 V, 30 Hz

Question 4

What is the power factor for an RLC series at resonance?

Accepted Answer

A)  one 
B)  its value depends upon the ratio of inductive reactance to impedance 
C)  its value depends upon the ratio of capacitive reactance to impedance 
D)  zero 
A)  one 
B)  its value depends upon the ratio of inductive reactance to impedance 
C)  its value depends upon the ratio of capacitive reactance to impedance 
D)  zero

Question 5

What is the inductive reactance of a 200 mH inductor attached to a 120 V rms, 60.0 Hz source?

Accepted Answer

A)  12.0 Ω 
B)  75.4 Ω 
C)  188 Ω 
D)  940 Ω 
E)  24.0 Ω 
A)  12.0 Ω 
B)  75.4 Ω 
C)  188 Ω 
D)  940 Ω 
E)  24.0 Ω

Question 6

In an RLC series circuit, which of the following statements is true?

Accepted Answer

A)  The current is in phase with the voltage across the inductor. 
B)  The current is in phase with the voltage across the resistor. 
C)  The current is in phase with the voltage across the capacitor. 
D)  None of the choices are true. 
A)  The current is in phase with the voltage across the inductor. 
B)  The current is in phase with the voltage across the resistor. 
C)  The current is in phase with the voltage across the capacitor. 
D)  None of the choices are true.

Question 7

What is the rms current for an 8.0 μF capacitor attached to a 120 V rms 60 Hz source?

Accepted Answer

A)  2.8 A 
B)  1.4 A 
C)  0.72 A 
D)  0.36 A 
E)  0.18 A 
A)  2.8 A 
B)  1.4 A 
C)  0.72 A 
D)  0.36 A 
E)  0.18 A

Question 8

The voltage supplied to an ac circuit is given by v(t) = (120 V) sin (377t). What is the voltage at t = 3.00 × 10−3 s?

Accepted Answer

A)  0.00 V 
B)  2.37 V 
C)  63.0 V 
D)  109 V 
E)  119 V 
A)  0.00 V 
B)  2.37 V 
C)  63.0 V 
D)  109 V 
E)  119 V

Question 9

An ac circuit consists of a 220 mH inductor in series with a 75 kΩ resistor and a 12 V rms sinusoidal emf. If the frequency of the emf is 25 kHz, what is the rms voltage across the resistor?

Accepted Answer

A)  7.0 V 
B)  9.4 V 
C)  11 V 
D)  5.0 V 
A)  7.0 V 
B)  9.4 V 
C)  11 V 
D)  5.0 V

Question 10

In a series RLC circuit the rms voltage across the resistor is 80.0 V, across the capacitor is 120 V, and across the inductor is 60.0 V. If 1.50 A rms current is flowing in this circuit, what is the average power dissipated?

Accepted Answer

A)  200 W 
B)  120 W 
C)  80.0 W 
D)  60.0 W 
E)  40.0 W 
A)  200 W 
B)  120 W 
C)  80.0 W 
D)  60.0 W 
E)  40.0 W

Question 11

The difference between the highest and lowest voltage of a household "120 V emf" is

Accepted Answer

A)  120 V. 
B)  170 V. 
C)  240 V. 
D)  340 V. 
E)  377 V. 
A)  120 V. 
B)  170 V. 
C)  240 V. 
D)  340 V. 
E)  377 V.

Question 12

What is the inductance of an inductor with a reactance of 20 Ω at a frequency of 60 Hz?

Accepted Answer

A)  12 H 
B)  19 H 
C)  3.0 H 
D)  53 mH 
E)  27 mH 
A)  12 H 
B)  19 H 
C)  3.0 H 
D)  53 mH 
E)  27 mH

Question 13

An RLC series circuit has a 200 Ω resistance, a 3.0 mH inductor, and a 100 μF capacitor. At resonance, what is the inductive reactance?

Accepted Answer

A)  21 Ω 
B)  5.5 Ω 
C)  11 Ω 
D)  25 Ω 
E)  30 Ω 
A)  21 Ω 
B)  5.5 Ω 
C)  11 Ω 
D)  25 Ω 
E)  30 Ω

Question 14

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 power factor?

Accepted Answer

A)  0 
B)  0.25 
C)  0.50 
D)  0.75 
E)  1.0 
A)  0 
B)  0.25 
C)  0.50 
D)  0.75 
E)  1.0

Question 15

A capacitor is connected to the terminals of a variable frequency oscillator. The peak voltage of the source is kept fixed while the frequency is increased. Which statement is true?

Accepted Answer

A)  The rms current through the capacitor decreases. 
B)  The rms current through the capacitor increases. 
C)  The phase angle between the current and source voltage changes. 
D)  The current becomes zero when the frequency is large enough. 
A)  The rms current through the capacitor decreases. 
B)  The rms current through the capacitor increases. 
C)  The phase angle between the current and source voltage changes. 
D)  The current becomes zero when the frequency is large enough.

Question 16

In a series RLC circuit the rms voltage across the resistor is 80 V, across the capacitor is 120 V, and across the inductor is 60 V. What is the phase constant for this circuit?

Accepted Answer

A)  27° 
B)  −27° 
C)  37° 
D)  −37° 
E)  −41° 
A)  27° 
B)  −27° 
C)  37° 
D)  −37° 
E)  −41°

Question 17

If the power factor for a series RLC circuit is 1.0, what is the phase constant?

Accepted Answer

A)  0.0° 
B)  30° 
C)  45° 
D)  60° 
E)  90° 
A)  0.0° 
B)  30° 
C)  45° 
D)  60° 
E)  90°

Question 18

As frequency is varied in an RLC series circuit, resonance is reached when

Accepted Answer

A)  the impedance becomes zero. 
B)  the inductive reactance is equal to the capacitive reactance. 
C)  the sum of the inductive and capacitive reactances is equal to the resistance. 
D)  the capacitive reactance is equal to the resistance. 
E)  the inductive reactance is equal to the resistance. 
A)  the impedance becomes zero. 
B)  the inductive reactance is equal to the capacitive reactance. 
C)  the sum of the inductive and capacitive reactances is equal to the resistance. 
D)  the capacitive reactance is equal to the resistance. 
E)  the inductive reactance is equal to the resistance.

Question 19

If the inductance and the capacitance both double in an LRC series circuit, the resonant frequency of that circuit will

Accepted Answer

A)  decrease by a factor of 1/2. 
B)  decrease by a factor of 1/4. 
C)  increase by a factor of 2. 
D)  increase by a factor of 4. 
A)  decrease by a factor of 1/2. 
B)  decrease by a factor of 1/4. 
C)  increase by a factor of 2. 
D)  increase by a factor of 4.

Question 20

What is the capacitive reactance of an 8.00 μF capacitor attached to 120 V rms at 60.0 Hz?

Accepted Answer

A)  166 Ω 
B)  332 Ω 
C)  663 Ω 
D)  480 Ω 
E)  960 Ω 
A)  166 Ω 
B)  332 Ω 
C)  663 Ω 
D)  480 Ω 
E)  960 Ω

Exam 21: Alternating Current

What inductance is needed in series with a 4.7 μF capacitor for a resonant frequency of 10 kHz?

An ac circuit has a resistance of 120 Ω and an impedance of 200 Ω. What is the power factor for this circuit?

The voltage supplied to an ac circuit is given by v(t) = (120 V) sin (60t). What are the rms voltage and the frequency?

What is the power factor for an RLC series at resonance?

What is the inductive reactance of a 200 mH inductor attached to a 120 V rms, 60.0 Hz source?

In an RLC series circuit, which of the following statements is true?

What is the rms current for an 8.0 μF capacitor attached to a 120 V rms 60 Hz source?

The voltage supplied to an ac circuit is given by v(t) = (120 V) sin (377t). What is the voltage at t = 3.00 × 10−3 s?

An ac circuit consists of a 220 mH inductor in series with a 75 kΩ resistor and a 12 V rms sinusoidal emf. If the frequency of the emf is 25 kHz, what is the rms voltage across the resistor?

In a series RLC circuit the rms voltage across the resistor is 80.0 V, across the capacitor is 120 V, and across the inductor is 60.0 V. If 1.50 A rms current is flowing in this circuit, what is the average power dissipated?

The difference between the highest and lowest voltage of a household "120 V emf" is

What is the inductance of an inductor with a reactance of 20 Ω at a frequency of 60 Hz?

An RLC series circuit has a 200 Ω resistance, a 3.0 mH inductor, and a 100 μF capacitor. At resonance, what is the inductive reactance?

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 power factor?

A capacitor is connected to the terminals of a variable frequency oscillator. The peak voltage of the source is kept fixed while the frequency is increased. Which statement is true?

In a series RLC circuit the rms voltage across the resistor is 80 V, across the capacitor is 120 V, and across the inductor is 60 V. What is the phase constant for this circuit?

If the power factor for a series RLC circuit is 1.0, what is the phase constant?

As frequency is varied in an RLC series circuit, resonance is reached when

If the inductance and the capacitance both double in an LRC series circuit, the resonant frequency of that circuit will

What is the capacitive reactance of an 8.00 μF capacitor attached to 120 V rms at 60.0 Hz?

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The voltage supplied to an ac circuit is given by v(t) = (120 V) sin (377t). What is the voltage at t = 3.00 × 10⁻³ s?