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Electrical Engineering Objective Questions { Complex AC }

1.  The area of a sinusoidal wave over a half-cycle is
A. max. value 2
B. 2 x max. value
C. max. value + IL
D. max. value 4-2n

2.  Alternating voltages and currents are expressed in r.m.s. values because
A. they can be easily determined
B. calculations become very simple
C. they give comparison with d.c.
D. none of the above

3.  The average value of sin20 over a complete cycle is
B. ?1
C. 1/2
D. zero

4.  The form factor of a sinusoidal wave is

5. Three parallel circuits take the following currents : = sin 3141; i2 = 30 sin (324t +7c/2); i3 = 25 sin (314t ? n/2) The expression for the resultant current is
A. 25 sin (314 t + n/3)
B. 5 sin (314 t + n/2)
C. 10 sin (314 t ? n/6)
D. 5 ri sin (314 t + n/4)

6. Each of the three coils generates an e.m.f. of 230 V. The e.m.f. of second leads that of the first by 120? and the third lags behind the first by the same angle. The resultant e.m.f. across the series combination of the coils is
B.230 V
C. 690 V
D. none of the above

7. In a pure resistive circuit, the instantaneous voltage and current are given by : v = 250 sin 3141 volts i = 10 sin 3141 amperes The peak power in the circuit is
A. 1250 W
B. 25 W
C. 2500W
D. 250 W

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