Question 1

In a simple series RC circuit with a sinusoidal driving voltage, the phase relationship for a capacitor is that the

Accepted Answer

A)   current leads the voltage by 90°.
B)   voltage leads the current by 90°.
C)   Either response might be correct, depending on further details.
D)   The voltage and current are in phase.

Question 2

The power factor for an RLC circuit is

Accepted Answer

A)   sin  θ	hetaθ  .
B)   cos  θ	hetaθ 
C)   tan  θ	hetaθ 
D)   cot  θ	hetaθ

Question 3

The resonant frequency of a 1-H inductor and 1-F capacitor (forming an LC circuit)  is

Accepted Answer

A)   0.16 Hz.
B)   1 Hz.
C)   1.2 Hz.
D)   1.4 Hz.

Question 4

In a simple series AC circuit, an explanation for the phase relationship between current and voltage for a capacitor is that the voltage across a capacitor is proportional to

Accepted Answer

A)   the current.
B)   the time integral of the current.
C)   the time derivative of the current.
D)   none of the above.

Question 5

A transformer has 90 turns on the primary coil and 175 turns on the secondary coil. If the AC input current is 5 A, the output current is

Accepted Answer

A)   2.6 A.
B)   9.7 A.
C)   3.5 A.
D)   7.8 A.

Question 6

A charged 200-  μ\muμ  F capacitor is connected to a 100-mH inductor to form an LC oscillator. The voltage across the inductor oscillates at

Accepted Answer

A)   210 Hz.
B)   120 Hz.
C)   36 Hz.
D)   82 Hz.

Question 7

An RLC circuit has a 12-  Ω\OmegaΩ  resistor connected to an inductor with 44  Ω\OmegaΩ  reactance and a capacitor with 21  Ω\OmegaΩ  reactance. The effective resistance as seen by the source (impedance)  is

Accepted Answer

A)   26  Ω\OmegaΩ 
B)   12  Ω\OmegaΩ 
C)   23  Ω\OmegaΩ 
D)   21  Ω\OmegaΩ

Question 8

Consider an ideal inductor L connected directly to an AC voltage source V, with I being the current in the loop. Summing voltage drops around the loop yields

Accepted Answer

A)    dI/dt=V/Ld I / d t = V / LdI/dt=V/L 
B)    dV/dt=I/Ld V / d t = I / LdV/dt=I/L 
C)    dV/dt=L/Id V / d t = L / IdV/dt=L/I 
D)    dI/dt=L/Vd I / d t = L / VdI/dt=L/V

Question 9

As the impedance in a simple series AC circuit gets larger, all of the following statements are valid except

Accepted Answer

A)   for a given AC current, the AC voltage increases.
B)   for a given AC power, the AC current decreases.
C)   for a given AC voltage, the AC current decreases.
D)   for a given AC voltage, the AC power increases.

Question 10

The instantaneous power loss in a circuit containing a resistor and an inductor through which DC current flows is given by the formula P = I2 Z. To retain the form of this equation for the case of AC current, it is enough to

Accepted Answer

A)   interpret P as average power.
B)   interpret I as rms current.
C)   Both of the first two answers are necessary and sufficient.
D)   Both of the first two answers are necessary, but they are not sufficient.

Question 11

A possible clue to question 35 is that the electrical element that exhibits "inertia to the change of the current" is the

Accepted Answer

A)   inductor.
B)   capacitor.
C)   Either of the previous responses is valid.
D)   None of the previous responses is valid.

Question 12

A 45-VAC signal (rms)  is present across a 5-  Ω\OmegaΩ  resistor. The time-averaged power dissipated in the resistor is

Accepted Answer

A)   400 W.
B)   800 W.
C)   200 W.
D)   100 W.

Question 13

RMS voltage is related to peak voltage by the equation

Accepted Answer

A)   Vrms = Vpeak.
B)   Vrms = Vpeak/  2\sqrt { 2 }2c-2.7,0,-7.17,-2.7,-13.5,-8c-5.8,-5.3,-9.5,-10,-9.5,-14c0,-2,0.3,-3.3,1,-4c1.3,-2.7,23.83,-20.7,67.5,-54c44.2,-33.3,65.8,-50.3,66.5,-51c1.3,-1.3,3,-2,5,-2c4.7,0,8.7,3.3,12,10s173,378,173,378c0.7,0,35.3,-71,104,-213c68.7,-142,137.5,-285,206.5,-429c69,-144,104.5,-217.7,106.5,-221l0 -0c5.3,-9.3,12,-14,20,-14H400000v40H845.2724s-225.272,467,-225.272,467s-235,486,-235,486c-2.7,4.7,-9,7,-19,7c-6,0,-10,-1,-12,-3s-194,-422,-194,-422s-65,47,-65,47zM834 80h400000v40h-400000z'/>​  .
C)   Vrms = Vpeak/2.
D)   Vrms = Vpeak/4.

Question 14

In an ideal transformer, the output

Accepted Answer

A)   voltage cannot exceed the input voltage.
B)   current cannot exceed the input current.
C)   power cannot exceed the input power.
D)   Each of the previous responses is valid.

Question 15

A transformer has 90 turns on the primary coil and 175 turns on the secondary coil. If the input voltage is 120 VAC, the output voltage is

Accepted Answer

A)   62 VAC.
B)   92 VAC.
C)   230 VAC.
D)   180 VAC.

Question 16

At high frequencies, the reactances of an inductor and capacitor are

Accepted Answer

A)   both large.
B)   large and small, respectively.
C)   small and large, respectively.
D)   both small.

Question 17

The rms emf across an inductor is 5.2 V, and the reactance of the inductor is 0.77  Ω\OmegaΩ  . The current (rms)  through the inductor is

Accepted Answer

A)   1.5 A.
B)   6.8 A.
C)   510 mA.
D)   150 mA.

Question 18

The quality factor, Q, of an ideal LC circuit oscillating at  ω0=100\omega _ { 0 } = 100ω0​=100  rad/s with an inductor (L)  of 120 mH is

Accepted Answer

A)   120.
B)  6/5.
C)   100
D)  infinite.

Question 19

The maximum (instantaneous)  emf across a capacitor is 160 V and the reactance of the capacitor is 12  Ω\OmegaΩ  . The maximum current through the capacitor is

Accepted Answer

A)   22 A.
B)   77 mA.
C)   13 A.
D)   5.2 A.

Question 20

In the transfer of electrical energy over power lines, it is desirable to minimize Joule heating. Therefore it is desirable to reduce the

Accepted Answer

A)   resistance.
B)   voltage.
C)   current.
D)   both (a)  and (c) .

Exam 32: Alternating Current Circuits

Consider an ideal inductor L connected directly to an AC voltage source V, with I being the current in the loop. Summing voltage drops around the loop yields

Correct AnswerverifiedShow Answer

A charged 200- μ\muμ F capacitor is connected to a 100-mH inductor to form an LC oscillator. The voltage across the inductor oscillates at

Correct AnswerverifiedShow Answer

At high frequencies, the reactances of an inductor and capacitor are

Correct AnswerverifiedShow Answer

A possible clue to question 35 is that the electrical element that exhibits "inertia to the change of the current" is the

Correct AnswerverifiedShow Answer

An RLC circuit has a 12- Ω\OmegaΩ resistor connected to an inductor with 44 Ω\OmegaΩ reactance and a capacitor with 21 Ω\OmegaΩ reactance. The effective resistance as seen by the source (impedance) is

Correct AnswerverifiedShow Answer

A transformer has 90 turns on the primary coil and 175 turns on the secondary coil. If the AC input current is 5 A, the output current is

Correct AnswerverifiedShow Answer

RMS voltage is related to peak voltage by the equation

Correct AnswerverifiedShow Answer

The quality factor, Q, of an ideal LC circuit oscillating at ω0=100\omega _ { 0 } = 100ω0​=100 rad/s with an inductor (L) of 120 mH is

Correct AnswerverifiedShow Answer

The rms emf across an inductor is 5.2 V, and the reactance of the inductor is 0.77 Ω\OmegaΩ . The current (rms) through the inductor is

Correct AnswerverifiedShow Answer

A 45-VAC signal (rms) is present across a 5- Ω\OmegaΩ resistor. The time-averaged power dissipated in the resistor is

Correct AnswerverifiedShow Answer

As the impedance in a simple series AC circuit gets larger, all of the following statements are valid except

Correct AnswerverifiedShow Answer

In an ideal transformer, the output

Correct AnswerverifiedShow Answer

A transformer has 90 turns on the primary coil and 175 turns on the secondary coil. If the input voltage is 120 VAC, the output voltage is

Correct AnswerverifiedShow Answer

In the transfer of electrical energy over power lines, it is desirable to minimize Joule heating. Therefore it is desirable to reduce the

Correct AnswerverifiedShow Answer

The instantaneous power loss in a circuit containing a resistor and an inductor through which DC current flows is given by the formula P = I2 Z. To retain the form of this equation for the case of AC current, it is enough to

Correct AnswerverifiedShow Answer

The power factor for an RLC circuit is

Correct AnswerverifiedShow Answer

The maximum (instantaneous) emf across a capacitor is 160 V and the reactance of the capacitor is 12 Ω\OmegaΩ . The maximum current through the capacitor is

Correct AnswerverifiedShow Answer

The resonant frequency of a 1-H inductor and 1-F capacitor (forming an LC circuit) is

Correct AnswerverifiedShow Answer

In a simple series RC circuit with a sinusoidal driving voltage, the phase relationship for a capacitor is that the

Correct AnswerverifiedShow Answer

In a simple series AC circuit, an explanation for the phase relationship between current and voltage for a capacitor is that the voltage across a capacitor is proportional to

Correct AnswerverifiedShow Answer

Correct Answer
verified

A charged 200- $\mu$ F capacitor is connected to a 100-mH inductor to form an LC oscillator. The voltage across the inductor oscillates at

Correct Answer
verified

Correct Answer
verified

Correct Answer
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An RLC circuit has a 12- $\Omega$ resistor connected to an inductor with 44 $\Omega$ reactance and a capacitor with 21 $\Omega$ reactance. The effective resistance as seen by the source (impedance) is

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

The quality factor, Q, of an ideal LC circuit oscillating at $\omega _ { 0 } = 100$ rad/s with an inductor (L) of 120 mH is

Correct Answer
verified

The rms emf across an inductor is 5.2 V, and the reactance of the inductor is 0.77 $\Omega$ . The current (rms) through the inductor is

Correct Answer
verified

A 45-VAC signal (rms) is present across a 5- $\Omega$ resistor. The time-averaged power dissipated in the resistor is

Correct Answer
verified

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
verified

The instantaneous power loss in a circuit containing a resistor and an inductor through which DC current flows is given by the formula P = I² Z. To retain the form of this equation for the case of AC current, it is enough to

Correct Answer
verified

Correct Answer
verified

The maximum (instantaneous) emf across a capacitor is 160 V and the reactance of the capacitor is 12 $\Omega$ . The maximum current through the capacitor is

Correct Answer
verified

Correct Answer
verified

Correct Answer
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Correct Answer
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