Question 1

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 2

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 3

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

Accepted Answer

A)  the voltages VR,VL and VC all become equal. 
B)  the voltages VL and VC become zero. 
C)  the voltage VR becomes equal to the source voltage. 
D)  None of the choices are correct. 
A)  the voltages VR,VL and VC all become equal. 
B)  the voltages VL and VC become zero. 
C)  the voltage VR becomes equal to the source voltage. 
D)  None of the choices are correct.

Question 4

An RLC series circuit has a 400 $\Omega$ resistance,a 2.5 mH inductor,and a capacitor.If the circuit is in resonance at 30 kHz,what is the capacitive reactance?

Accepted Answer

A)  4.0 $\times$ 102 $\Omega$ 
B)  6.2 $\times$ 102 $\Omega$ 
C)  4.7 $\times$ 102 $\Omega$ 
D)  71 $\Omega$ 
E)  0.00 
A)  4.0 $\times$ 102 $\Omega$ 
B)  6.2 $\times$ 102 $\Omega$ 
C)  4.7 $\times$ 102 $\Omega$ 
D)  71 $\Omega$ 
E)  0.00

Question 5

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

Accepted Answer

A)  maximum 
B)  1/2 maximum 
C)  0.707 maximum 
D)  zero 
A)  maximum 
B)  1/2 maximum 
C)  0.707 maximum 
D)  zero

Question 6

An RLC series circuit has a 200 $\Omega$ resistance,a 3.00 mH inductor,and a 100 $\mu$F capacitor.What is the resonant frequency for this circuit?

Accepted Answer

A)  1.80 kHz 
B)  1.80 MHz 
C)  290 Hz 
D)  290 kHz 
E)  11.0 kHz 
A)  1.80 kHz 
B)  1.80 MHz 
C)  290 Hz 
D)  290 kHz 
E)  11.0 kHz

Question 7

A series LR circuit dissipates 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 phase constant?

Accepted Answer

A)  14$^{\circ}$ 
B)  25$^{\circ}$ 
C)  60$^{\circ}$ 
D)  70$^{\circ}$ 
E)  76$^{\circ}$ 
A)  14$^{\circ}$ 
B)  25$^{\circ}$ 
C)  60$^{\circ}$ 
D)  70$^{\circ}$ 
E)  76$^{\circ}$

Question 8

A 1500 W hair dryer is run on a 120 V rms circuit.If the circuit breaker is chosen from breakers with the ratings below,which is the lowest-rated current breaker of the following 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 9

A 25 nH inductor is in an AC circuit whose generator has an rms voltage of 12 V.At what frequency must the generator drive the circuit if the rms current is to be 2.0 mA?

Accepted Answer

A)  0.15 MHz 
B)  38 GHz 
C)  0.96 MHz 
D)  240 GHz 
A)  0.15 MHz 
B)  38 GHz 
C)  0.96 MHz 
D)  240 GHz

Question 10

A 150 W light bulb is designed for an ac voltage of 120 V rms.What is the resistance of the bulb?

Accepted Answer

A)  150 $\Omega$ 
B)  144 $\Omega$ 
C)  96.0 $\Omega$ 
D)  68.0 $\Omega$ 
E)  48.0 $\Omega$ 
A)  150 $\Omega$ 
B)  144 $\Omega$ 
C)  96.0 $\Omega$ 
D)  68.0 $\Omega$ 
E)  48.0 $\Omega$

Question 11

What is the peak (maximum)power dissipated by a 150 W light bulb attached to a 120 V rms ac line?

Accepted Answer

A)  301 W 
B)  212 W 
C)  150 W 
D)  106 W 
E)  75.0 W 
A)  301 W 
B)  212 W 
C)  150 W 
D)  106 W 
E)  75.0 W

Question 12

A series LR circuit dissipates 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 circuit resistance?

Accepted Answer

A)  50 $\Omega$ 
B)  60 $\Omega$ 
C)  15 $\Omega$ 
D)  10 $\Omega$ 
E)  24 $\Omega$ 
A)  50 $\Omega$ 
B)  60 $\Omega$ 
C)  15 $\Omega$ 
D)  10 $\Omega$ 
E)  24 $\Omega$

Question 13

In an ac circuit,the current in an inductor

Accepted Answer

A)  leads the voltage by 90$\circ$. 
B)  lags the voltage by 90$\circ$. 
C)  is in phase with the voltage. 
D)  leads the voltage by $\pi$ radians. 
E)  lags the voltage by $\pi$ radians. 
A)  leads the voltage by 90$\circ$. 
B)  lags the voltage by 90$\circ$. 
C)  is in phase with the voltage. 
D)  leads the voltage by $\pi$ radians. 
E)  lags the voltage by $\pi$ radians.

Exam 21: Alternating Current

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

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

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

An RLC series circuit has a 400 Ω\OmegaΩ resistance,a 2.5 mH inductor,and a capacitor.If the circuit is in resonance at 30 kHz,what is the capacitive reactance?

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

An RLC series circuit has a 200 Ω\OmegaΩ resistance,a 3.00 mH inductor,and a 100 μ\muμ F capacitor.What is the resonant frequency for this circuit?

A series LR circuit dissipates 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 phase constant?

A 1500 W hair dryer is run on a 120 V rms circuit.If the circuit breaker is chosen from breakers with the ratings below,which is the lowest-rated current breaker of the following that won't open the circuit?

A 25 nH inductor is in an AC circuit whose generator has an rms voltage of 12 V.At what frequency must the generator drive the circuit if the rms current is to be 2.0 mA?

A 150 W light bulb is designed for an ac voltage of 120 V rms.What is the resistance of the bulb?

What is the peak (maximum)power dissipated by a 150 W light bulb attached to a 120 V rms ac line?

A series LR circuit dissipates 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 circuit resistance?

In an ac circuit,the current in an inductor

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An RLC series circuit has a 400 $\Omega$ resistance,a 2.5 mH inductor,and a capacitor.If the circuit is in resonance at 30 kHz,what is the capacitive reactance?

An RLC series circuit has a 200 $\Omega$ resistance,a 3.00 mH inductor,and a 100 $\mu$ F capacitor.What is the resonant frequency for this circuit?