AC Fundamentals - Electronics Engineering test questions
(1) It is said that the two sinusoidal quantities are in phase quadrature when their phase difference is(A) 30°
(B) 0°
(C) 90°
(D) 45°
View Answer / Hide Answer(2) Consider a current sine wave whose rms value is 30 amperes. The equation for 25 cycles current sine wave will be(A) 42.4 sin 50 π t
(B) 42.4 sin 25 π t
(C) 30 sin 50 π t
(D) 30 sin 50 π t
View Answer / Hide Answer(3) If E1 = A sin ωt and E2 = A sin (ωt – Φ), then(A) E1 leads E2 by Φ
(B) E1 lags E2 by Φ/2
(C) E2 leads E1 by Φ
(D) E2 lags E1 by Φ
View Answer / Hide Answer(4) _____________ is the rms value of rectangular voltage wave with and amplitude of 10 V.(A) 11.2 V
(B) 5.2 V
(C) 7.7 V
(D) 10 V
View Answer / Hide Answer(5) Consider 220 V, 50 Hz A.C. waveform. The form factor will be(A) 1.5
(B) 1.11
(C) 1.14
(D) 0.85
View Answer / Hide Answer(6) Let i = 100 sin ωt. How long will it take for the current to rise to 50 amperes if the frequency is 25 Hz?(A) 1/30 sec
(B) 1/50 sec
(C) 1/1000 sec
(D) 1/100 sec
View Answer / Hide Answer(7) Voltage V = 90 cos (ωt-161.5°). This may be represented as sine function by(A) 90 sin (ωt – 18.5°)
(B) 90 sin (ωt + 18.5°)
(C) 90 sin (ωt + 71.5°)
(D) 90 sin (ωt – 71.5°)
View Answer / Hide AnswerANSWER: 90 sin (ωt – 71.5°)
(A) 10.6 A
(B) 10 A
(C) 8 A
(D) 15 A
View Answer / Hide Answer(9) The negative maximum of a cosine waveform occurs at (A) 0°
(B) 270°
(C) 180°
(D) 90°
View Answer / Hide Answer(10) Let us say that the current and voltage both are out of phase by 90°. The power will be (A) Maximum
(B) Minimum
(C) Zero
(D) 1.1 VI
View Answer / Hide Answer(11) Which one of the following has the least value of form factor?(A) Sine wave
(B) Square wave
(C) Rectangular wave
(D) Triangular wave
View Answer / Hide Answer(12) The frequency that has the longest period is(A) 10 KHz
(B) 1 KHz
(C) 10 Hz
(D) 1 Hz
View Answer / Hide Answer(13) The waveform that has the least rms value for the same peak value of voltage is(A) Triangular wave
(B) Sine wave
(C) Square wave
(D) Full wave rectified sine wave
View Answer / Hide Answer(14) Which of the following statement is false?(A) The 480° vector will end up in second quadrant
(B) Every non-sinusoidal waveform has large number of harmonics
(C) A square wave has only even harmonics
(D) All of the above statements are true
View Answer / Hide AnswerANSWER: All of the above statements are true
For questions 15 to 17 refer to the following data:
For equal intervals of time, a current has following steady values in amperes changing simultaneously from one to the next
0,10,20,30,20,10,0, -10, -20, -30, -20, -10, -0
(15) The rms value of current will be(A) 10 A
(B) 17.8 A
(C) 178 A
(D) 100 A
View Answer / Hide Answer(16) The form factor will be(A) 1.187
(B) 1.0
(C) 1.100
(D) 1.11
View Answer / Hide Answer(17) The peak factor of a wave is(A) Rms value / average value
(B) Average value / rms value
(C) Maximum value / rms value
(D) Maximum value / average value
View Answer / Hide AnswerANSWER: Maximum value / rms value
(A) 1.33 sec
(B) 133 sec
(C) 1.33 micro-second
(D) 1.33 milli-second
View Answer / Hide AnswerANSWER: 1.33 milli-second
(A) Draw less current
(B) Draw more current
(C) Draw less current but power will be less
(D) Nothing will happen
View Answer / Hide AnswerANSWER: Draw more current
(A) 0.866 leading
(B) 0.866 lagging
(C) 30 leading
(D) None of the above
View Answer / Hide Answer(21) A certain square wave has a period of 4 ms. Its fundamental frequency will be (A) 0 Hz
(B) 230 Hz
(C) 250 Hz
(D) 430 Hz
View Answer / Hide Answer
