Circuit Analysis

Question 1

A lightbulb is rated for 65 W and 120 V. Calculate its resistance and operating current.

A. 1.85 space straight capital omega comma space space 35.2 space straight A

B. 221.5 space straight capital omega comma space space 35.2 space straight A

C. 1.85 space straight capital omega comma space space 0.542 space straight A

D. 221.5 space straight capital omega comma space space 0.542 space straight A

Answer 1

Correct Option: D

Question 2

What are the average and root-mean-squared (RMS) values of an irregular pulse train that repeats every 30 ms? A total of 8 pulses occur during any 30 ms cycle. Assume the duration of pulses is 2 ms and the amplitude of pulses is 5 V.

A. Vavg space end subscript equals 3 space straight V comma space straight V subscript RMS space equals space 1.67 space straight V

B. Vavg space equals space minus 1.5 space straight V comma space straight V subscript RMS space equals space 2.54 space straight V

C. V avg space equals space 2.67 space straight V comma space straight V subscript RMS space end subscript equals space 3.65 space straight V

D. Vavg = -2 V, VRMS = 3 V

Answer 2

Correct Option: C

Question 3

Determine the root-mean-squared (RMS) value of the sum of currents if a voltage of 15cos (200t + 15degree) is applied to a 35-ohm resistor and a 2.5-H inductor that are arranged in parallel.

A. 1.56 A

B. 0.3 A

C. 0.41 A

D. 2.15 A

Answer 3

Correct Option: B

Question 4

A meter movement has an internal resistance of 5 k ohms and a full-scale current of 50 µA. The movement is to be used within a voltmeter with a full-scale voltage of 20V. A resistance in series with the movement will be used to limit full-scale meter indications. Most nearly, the value of the series resistance is:

A. 2k ohms.

B. 5k ohms.

C. 400k ohms.

D. 500k ohms.

Question 5

The voltage for a waveform is 2 V + (5 V)(cos2πt). Most nearly, the effective value of this waveform is

A. 3.0 V.

B. 4.1 V.

C. 5.5 V.

D. 7.0 V.

Answer 5

Correct Option: B

Question 6

A wire carries an AC current of 3cos100πt A. What is the average current over 6 s?

A. 0 A

B. π/6 A

C. 1.5 A

D. 6/π A

Answer 6

Correct Option: A

Question 7

A voltage of 20 cos (50t + 10°) is applied to a resistance of 25Ω and an inductance of 0.2 henrys in parallel. Find the RMS and phase angle of the sum of currents?

A. 2.52A, -14°

B. 3.11A, 14°

C. 1.52A, -58°

D. 4.12 A, 58°

Answer 7

Correct Option: C

Question 8

Given that Z = 100 + j50Ω, how many degrees does the current lag the voltage?

A. -26.57°

B. 26.57°

C. -111.80°

D. 111.80°

Answer 8

Correct Option: B

Question 9

Given a circuit with an impedance of 75 < 78°Ω, what is the resistance of the circuit?

A. 15.59Ω

B. 75Ω

C. 78Ω

D. 73.36Ω

Answer 9

Correct Option: A

Question 10

Find the RMS value of the following waveform that has a DC offset of 2V:

V = 11 × cos(ωt) + 5sin(5ωt) – 7cos(2ωt)

A. Vrms = 8.78

B. Vrms = 10.07

C. Vrms = 13.5

D. Vrms = 15.7

Answer 10

Correct Option: B

Question 11

What acts like an open circuit when exposed to a steady-state DC current?

A. Resistor

B. Reactor

C. Capacitor

D. Inductor

Answer 11

Correct Option: C

Question 12

Convert 53.7 + j26.5 MVA from rectangular form to polar form.

A. 59.88 ∟-26.27° MVA

B. 59.88 ∟26.27° MVA

C. 59.88 ∟60.43° MVA

D. 59.88 ∟63.73° MVA

Answer 12

Correct Option: B

Using Ohm’s law, the current is calculated as I = V/R.

To divide phasors, first divide the magnitude and then subtract the angles.

I = 120 ∟30°V / 30 ∟15° Ω = 4 ∟15°A

Question 13

Given an electromagnetic wave traveling in free space with a frequency of 13 GHz, what is the wavelength?

A. 110 mm

B. 23 mm

C. 30 mm

D. 76 mm

Answer 13

Correct Option: B