1. . Current (or voltage) is said to be alternating when it changes in:
(A) Magnitude only
(B) Direction only
(C) Both a and b
(D) None of these
2. . The working principle of the AC generator is:
(A) Electrostatics
(B) Magnetic locking
(C) Electrochemical
(D) Electromagnetic induction
3. . The number of cycles per second in any conductor is called:
(A) Frequency
(B) 1 cycle
(C) Time period
(D) 1 sec
4. . The unit of frequency is:
(A) Cycle
(B) Second
(C) Cycle/sec
(D) Sec/cycle
5. . Frequency in PAKISTAN is:
(A) 25 c/s
(B) 40 c/s
(C) 50 c/s
(D) 60 c/s
6. . The sine wave which completes 50 cycles per second, its frequency will be:
(A) 25 c/s
(B) 50 c/s
(C) 75 c/s
(D) 100 c/s
7. . One complete set of positive and negative values of an alternating quantity is known as:
(A) Waveform
(B) Cycle
(C) Amplitude
(D) Phasor
8. . During each cycle, a sine wave reaches a peak value:
(A) One time
(B) Two times
(C) Four times
(D) Depends on frequency
9. . If the frequency is 1 Hz, then time is:
(A) 4 sec
(B) 3 sec
(C) 2 sec
(D) 1 sec
10. . When a sine wave has a frequency of 60 Hz, in 10 s it goes through:
(A) 6 cycles
(B) 10 cycles
(C) 1/16 cycle
(D) 600 cycles
11. . 110 volts peak value is approximately equal to RMS value:
(A) 77 V
(B) 66 V
(C) 55 V
(D) 44 V
12. . The form factor is the ratio of:
(A) Peak value to RMS value
(B) RMS value to average value
(C) Average value to RMS value
(D) None
13. . A 10 V RMS value is approximately equal to peak value:
(A) 7 V
(B) 14 V
(C) 21 V
(D) 28 V
14. . A sine wave reaches maximum positive voltage at:
(A) 90°
(B) 0°
(C) –90°
(D) 360°
15. . Average value of 10 V peak sine wave over one complete cycle is:
(A) 0 V
(B) 6.37 V
(C) 7.07 V
(D) 5 V
16. . Average half-cycle value of sine wave with 20 V peak is:
(A) 0 V
(B) 6.37 V
(C) 12.74 V
(D) 14.14 V
17. . If the peak value of sine wave is 10 V, the peak-to-peak value is:
(A) 20 V
(B) 5 V
(C) 100 V
(D) 15 V
18. . If the peak value of sine wave is 20 V, the RMS value is:
(A) 14.14 V
(B) 6.37 V
(C) 7.07 V
(D) 0.707 V
19. . Value of an alternating current at any instant is:
(A) Maximum value
(B) Peak value
(C) Instantaneous value
(D) RMS value
20. . RMS value of the current in sine wave is:
(A) 0.707 Imax
(B) 7.07 Imax
(C) 0.636 Imax
(D) 6.36 Imax
21. . Average value of current in sine wave is:
(A) 6.36 Imax
(B) 0.636 Imax
(C) 7.07 Imax
(D) 0.707 Imax
22. . Time period of sine wave with frequency 50 c/s is:
(A) 5 sec
(B) 0.02 sec
(C) 25 sec
(D) 50 sec
23. . Sine wave equation of current can be written as:
(A) i = Imax sinΦ
(B) i = Imax sin ωt
(C) i = Imax sin 2πft
(D) All
24. . Ratio of RMS value to average value is called:
(A) Peak factor
(B) Form factor
(C) Crest factor
(D) Amplitude
25. . Form factor =
(A) Average / RMS
(B) RMS / Average
(C) Max / RMS
(D) Max / Average
26. . Ratio between RMS value and average value is called:
(A) Peak factor
(B) Form factor
(C) Crest factor
(D) Amplitude factor
27. . Value of form factor is:
(A) 1
(B) 1.11
(C) 1.414
(D) 0.707
28. . Value of peak-to-peak factor is:
(A) 1
(B) 1.11
(C) 1.414
(D) 0.707
29. . Maximum value of sine wave is 10 A, RMS value is:
(A) 7.07 A
(B) 10 A
(C) 14.14 A
(D) 28.28 A
30. . 50 c/s frequency sine wave has time period:
(A) 1/50 sec
(B) 5 sec
(C) 25 sec
(D) 50 sec
31. . When two AC waves with same frequency start & finish from same point, they are called:
(A) Phase
(B) Out of phase
(C) In-phase
(D) None
32. . Waveform behind the other waveform w.r.t time or angle is called:
(A) Lagging wave
(B) Leading wave
(C) Anti phase wave
(D) Phase quadrature wave
33. . Waveform ahead of the other waveform w.r.t time or angle is called:
(A) Lagging wave
(B) Leading wave
(C) Anti phase wave
(D) Phase quadrature wave