47 + Mcqs in Alternating Current And Voltage Page 1 McqOptions

1.	A signal with a 400 s period has a frequency of
A.	250 Hz
B.	2,500 Hz
C.	25,000 Hz
D.	400 Hz
Answer» C. 25,000 Hz

Discussion

2.	If the rms current through a 4.7 k resistor is 4 mA, the peak voltage drop across the resistor is
A.	4 V
B.	18.8 V
C.	26.6 V
D.	2.66 V
Answer» D. 2.66 V

Discussion

3.	If the rms current through a 6.8 k resistor is 8 mA, the rms voltage drop across the resistor is
A.	5.44 V
B.	54.4 V
C.	7.07 V
D.	8 V
Answer» C. 7.07 V

Discussion

4.	A square wave has a period of 60 s. The first odd harmonic is
A.	5 kHz
B.	50 kHz
C.	500 kHz
D.	33.33 kHz
Answer» C. 500 kHz

Discussion

5.	A 20 kHz pulse waveform consists of pulses that are 15 s wide. The duty cycle
A.	is 1%
B.	is 30%
C.	is 100%
D.	cannot be determined
Answer» C. is 100%

Discussion

6.	If the rms voltage drop across a 15 k resistor is 16 V, the peak current through the resistor is
A.	15 mA
B.	1.5 mA
C.	10 mA
D.	1 mA
Answer» C. 10 mA

Discussion

7.	How many degrees are there in /3 rad?
A.	6°
B.	60°
C.	180°
D.	27°
Answer» C. 180°

Discussion

8.	If the rms current through a 4.7 kΩ resistor is 4 mA, the peak voltage drop across the resistor is
A.	V
B.	8.8 V
C.	6.6 V
D.	.66 V
Answer» D. .66 V

Discussion

9.	If the rms current through a 6.8 kΩ resistor is 8 mA, the rms voltage drop across the resistor is
A.	.44 V
B.	4.4 V
C.	.07 V
D.	V
Answer» C. .07 V

Discussion

10.	A 20 kHz pulse waveform consists of pulses that are 15 µs wide. The duty cycle
A.	s 1%
B.	s 30%
C.	s 100%
D.	annot be determined
Answer» C. s 100%

Discussion

11.	Duty cycle is the characteristic of a pulse waveform that indicates the high time versus the low time.
A.	rue
B.	alse
Answer» C.

Discussion

12.	How many degrees are there in p/3 rad?
A.	°
B.	0°
C.	80°
D.	7°
Answer» C. 80°

Discussion

13.	The unit of frequency is the hertz.
A.	rue
B.	alse
Answer» B. alse

Discussion

14.	The angular position of a phasor represents the angle of the sine wave with respect to a reference.
A.	rue
B.	alse
Answer» B. alse

Discussion

15.	If the rms voltage drop across a 15 kΩ resistor is 16 V, the peak current through the resistor is
A.	5 mA
B.	.5 mA
C.	0 mA
D.	mA
Answer» C. 0 mA

Discussion

16.	The duty cycle of a pulse waveform with a pulse width of 10 µs and a period of 100 µs is 25%.
A.	rue
B.	alse
Answer» C.

Discussion

17.	A saw-tooth wave has a period of 10 ms. Its frequency is
A.	0 Hz
B.	0 Hz
C.	00 Hz
D.	,000 Hz
Answer» D. ,000 Hz

Discussion

18.	Periodic is characterized by a repetition at fixed time intervals.
A.	rue
B.	alse
Answer» B. alse

Discussion

19.	A square wave has a period of 60 µs. The first odd harmonic is
A.	kHz
B.	0 kHz
C.	00 kHz
D.	3.33 kHz
Answer» C. 00 kHz

Discussion

20.	A signal with a 400 µs period has a frequency of
A.	50 Hz
B.	,500 Hz
C.	5,000 Hz
D.	00 Hz
Answer» C. 5,000 Hz

Discussion

21.	The instantaneous value is the voltage or current value of a waveform at its peak.
A.	rue
B.	alse
Answer» C.

Discussion

22.	A 1 kHz signal has a period of 1 ms.
A.	rue
B.	alse
Answer» B. alse

Discussion

23.	If a sine wave goes through 10 cycles in 20 µs, the period is
A.	0 µs
B.	µs
C.	µs
D.	00 µs
Answer» D. 00 µs

Discussion

24.	A ramp is the type of waveform characterized by a non-linear increase or decrease in voltage or current.
A.	rue
B.	alse
Answer» C.

Discussion

25.	Sine wave A has a positive-going zero crossing at 45°. Sine wave B has a positive-going zero crossing at 60°. Which of the following statements is true?
A.	ave A leads wave B by 15°
B.	ave A lags wave B by 15°
C.	ave A leads wave B by 105°
D.	ave A lags wave B by 105°
Answer» B. ave A lags wave B by 15°

Discussion

26.	If a sine wave goes through 10 cycles in 20 s, the period is
A.	20 s
B.	4 s
C.	2 s
D.	100 s
Answer» D. 100 s

Discussion

27.	A sine wave of 15 kHz is changing at a faster rate than a sine wave with a frequency of
A.	25 kHz
B.	12 kHz
C.	18 kHz
D.	1.3 MHz
Answer» C. 18 kHz

Discussion

28.	A square wave has a period of 60 s. The first odd harmonic is
A.	5 kHz
B.	50 kHz
C.	500 kHz
D.	33.33 kHz
Answer» C. 500 kHz

Discussion

29.	The average half-cycle value of a sine wave with a 40 V peak is
A.	25.48 V
B.	6.37 V
C.	14.14 V
D.	50.96 V
Answer» B. 6.37 V

Discussion

30.	Amplitude is the maximum value of a voltage or current.
A.	1
B.
C.	1
D.
Answer» B.

Discussion

31.	A sine wave with an rms value of 12 V is riding on a dc level of 18 V. The maximum value of the resulting waveform is
A.	6 V
B.	30 V
C.	35 V
D.	0 V
Answer» D. 0 V

Discussion

32.	If the peak of a sine wave is 13 V, the peak-to-peak value is
A.	6.5 V
B.	13 V
C.	26 V
D.	none of the above
Answer» D. none of the above

Discussion

33.	Average value of a sine wave is 0.707 times the peak value.
A.	1
B.
Answer» C.

Discussion

34.	The average value of a 12 V peak sine wave over one complete cycle is
A.	0 V
B.	1.27 V
C.	7.64 V
D.	6.37 V
Answer» B. 1.27 V

Discussion

35.	The length of a phasor represents the amplitude.
A.	1
B.
C.	1
D.
Answer» B.

Discussion

36.	The designation rms means repetitions measured per second.
A.	1
B.
Answer» C.

Discussion

37.	Sine wave A has a positive-going zero crossing at 45¬∞. Sine wave B has a positive-going zero crossing at 60¬∞. Which of the following statements is true?
A.	Wave A leads wave B by 15¬∞.
B.	Wave A lags wave B by 15¬∞.
C.	Wave A leads wave B by 105¬∞.
D.	Wave A lags wave B by 105¬∞.
Answer» B. Wave A lags wave B by 15¬∞.

Discussion

38.	A signal with a 400 s period has a frequency of
A.	250 Hz
B.	2,500 Hz
C.	25,000 Hz
D.	400 Hz
Answer» C. 25,000 Hz

Discussion

39.	The duty cycle of a pulse waveform with a pulse width of 10 ¬µs and a period of 100 ¬µs is 25%.
A.	1
B.
C.	1
D.
Answer» C. 1

Discussion

40.	How many degrees are there in /3 rad?
A.	6¬∞
B.	60¬∞
C.	180¬∞
D.	27¬∞
Answer» C. 180¬∞

Discussion

41.	If the rms current through a 4.7 k resistor is 4 mA, the peak voltage drop across the resistor is
A.	4 V
B.	18.8 V
C.	26.6 V
D.	2.66 V
Answer» D. 2.66 V

Discussion

42.	One sine wave has a positive-going zero crossing at 15¬∞ and another sine wave has a positive-going zero crossing at 55¬∞. The phase angle between the two waveforms is
A.	0¬∞
B.	45¬∞
C.	40¬∞
D.	none of the above
Answer» D. none of the above

Discussion

43.	A sine wave with a period of 4 ms is changing at a faster rate than a sine wave with a period of
A.	0.0045 s
B.	2 ms
C.	1.5 ms
D.	3,000 s
Answer» B. 2 ms

Discussion

44.	To produce an 800 Hz sine wave, a four-pole generator must be operated at
A.	200 rps
B.	400 rps
C.	800 rps
D.	1,600 rps
Answer» C. 800 rps

Discussion

45.	Two series resistors are connected to an ac source. If there are 7.5 V rms across one resistor and 4.2 V rms across the other, the peak source voltage is
A.	16.54 V
B.	1.65 V
C.	10.60 V
D.	5.93 V
Answer» B. 1.65 V

Discussion

46.	The conductive loop on the rotor of a simple two-pole, single-phase generator rotates at a rate of 400 rps. The frequency of the induced output voltage is
A.	40 Hz
B.	100 Hz
C.	400 Hz
D.	indeterminable
Answer» D. indeterminable

Discussion

47.	If the rms voltage drop across a 15 k resistor is 16 V, the peak current through the resistor is
A.	15 mA
B.	1.5 mA
C.	10 mA
D.	1 mA
Answer» C. 10 mA

Discussion

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