Question 1

If the voltage amplitude across an 8.50-nF capacitor is equal to 12.0 V when the current amplitude through it is 3.33 mA,the frequency is closest to:

Accepted Answer

A)  32.6 MHz. 
B)  5.20 MHz. 
C)  32.6 kHz. 
D)  5.20 kHz. 
E)  32.6 Hz. 
A)  32.6 MHz. 
B)  5.20 MHz. 
C)  32.6 kHz. 
D)  5.20 kHz. 
E)  32.6 Hz.

Question 2

An ac source of period T and maximum voltage V is connected to a single unknown ideal element that is either a resistor,and inductor,or a capacitor.At time t = 0 the voltage is zero.At time t = T/4 the current in the unknown element is equal to zero,and at time t = T/2 the current is I = -Imax,where Imax is the current amplitude.What is the unknown element?

Accepted Answer

A)  a resistor 
B)  an inductor 
C)  a capacitor 
D)  an inductor or a capacitor 
A)  a resistor 
B)  an inductor 
C)  a capacitor 
D)  an inductor or a capacitor

Question 3

A series LRC ac circuit has a peak voltage of   and a peak current of   If the current lags the voltage by   what is the average power of the circuit?

Accepted Answer

A)  91 W 
B)  182 W 
C)  78 W 
D)  156 W 
A)  91 W 
B)  182 W 
C)  78 W 
D)  156 W

Question 4

A series circuit consists of a 50-Hz ac source,a 40-Ω resistor,a 0.30-H inductor,and a 60-μF capacitor.The rms current in the circuit is measured to be 1.6 A.What is the power factor of the circuit?

Accepted Answer

A)  0.70 
B)  0.66 
C)  0.63 
D)  0.59 
E)  0.56 
A)  0.70 
B)  0.66 
C)  0.63 
D)  0.59 
E)  0.56

Question 5

The phase angle of an LRC series circuit with an inductive reactance of 200 Ω and a capacitive reactance of 100 Ω is 40.0°.What is the value of the resistor in this circuit?

Accepted Answer

A)  100 Ω 
B)  119 Ω 
C)  156 Ω 
D)  200 Ω 
E)  265 Ω 
A)  100 Ω 
B)  119 Ω 
C)  156 Ω 
D)  200 Ω 
E)  265 Ω

Question 6

The 60-Hz ac source of a series circuit has a voltage amplitude of 120 V.The resistance,capacitive reactance,and inductive reactance are as shown in the figure.What is the rms current in the circuit?

Accepted Answer

A)  0.097 A 
B)  0.11 A 
C)  0.12 A 
D)  0.14 A 
E)  0.17 A 
A)  0.097 A 
B)  0.11 A 
C)  0.12 A 
D)  0.14 A 
E)  0.17 A

Question 7

An ac circuit is shown in the figure.The rms current in the circuit is measured to be 1.8 A.What is the capacitance of the capacitor?

Accepted Answer

A)  23 μF 
B)  24 μF 
C)  21 μF 
D)  19 μF 
E)  18 μF 
A)  23 μF 
B)  24 μF 
C)  21 μF 
D)  19 μF 
E)  18 μF

Question 8

An ac circuit is shown in the figure.The rms current in the circuit is 1.3 A.What is the peak magnetic energy in the inductance?

Accepted Answer

A)  0.32 J 
B)  0.16 J 
C)  0.48 J 
D)  0.64 J 
E)  0.80 J 
A)  0.32 J 
B)  0.16 J 
C)  0.48 J 
D)  0.64 J 
E)  0.80 J

Question 9

A series circuit consists of ac source,a 90-Ω resistor,a 0.80-H inductor,and an 80-μF capacitor.The frequency of the source is adjusted so that the capacitive reactance is equal to twice the inductive reactance.What is the frequency of the source?

Accepted Answer

A)  14 Hz 
B)  13 Hz 
C)  16 Hz 
D)  17 Hz 
E)  19 Hz 
A)  14 Hz 
B)  13 Hz 
C)  16 Hz 
D)  17 Hz 
E)  19 Hz

Question 10

When a current of 2.0 A flows in the 100-turn primary of an ideal transformer,this causes 14 A to flow in the secondary.How many turns are in the secondary?

Accepted Answer

A)  700 
B)  356 
C)  114 
D)  14 
E)  4 
A)  700 
B)  356 
C)  114 
D)  14 
E)  4

Exam 31: Alternating Current

If the voltage amplitude across an 8.50-nF capacitor is equal to 12.0 V when the current amplitude through it is 3.33 mA,the frequency is closest to:

A series LRC ac circuit has a peak voltage of and a peak current of If the current lags the voltage by what is the average power of the circuit?

A series circuit consists of a 50-Hz ac source,a 40-Ω resistor,a 0.30-H inductor,and a 60-μF capacitor.The rms current in the circuit is measured to be 1.6 A.What is the power factor of the circuit?

The phase angle of an LRC series circuit with an inductive reactance of 200 Ω and a capacitive reactance of 100 Ω is 40.0°.What is the value of the resistor in this circuit?

The 60-Hz ac source of a series circuit has a voltage amplitude of 120 V.The resistance,capacitive reactance,and inductive reactance are as shown in the figure.What is the rms current in the circuit?

An ac circuit is shown in the figure.The rms current in the circuit is measured to be 1.8 A.What is the capacitance of the capacitor?

An ac circuit is shown in the figure.The rms current in the circuit is 1.3 A.What is the peak magnetic energy in the inductance?

A series circuit consists of ac source,a 90-Ω resistor,a 0.80-H inductor,and an 80-μF capacitor.The frequency of the source is adjusted so that the capacitive reactance is equal to twice the inductive reactance.What is the frequency of the source?

When a current of 2.0 A flows in the 100-turn primary of an ideal transformer,this causes 14 A to flow in the secondary.How many turns are in the secondary?

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