Tuesday, September 1, 2020

Chapter 4: Complex AC Circuits- Page 1

Chapter 4: Complex AC Circuits

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

... Answer is (D)



2. Alternating voltages and currents are expressed in r.m.s. values because

A. calculations become very simple
B. they give comparison with d.c.
C. they can be easily determined
D. none of the above

... Answer is (B)


3. The average value of sin²θ over a complete cycle is

A. -1
B. +1

D. 1/2

... Answer is (D)



4. The form factor of a sinusoidal wave is

A. 1.414
B. 1.11
C. 2
D. 1.5

  ... Answer is (B)


5. 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
Answer is (C)


6. In a pure resistive circuit, the instantaneous voltage and current are given by : v = 250 sin 314t volts i = 10 sin 314 t amperes The peak power in the circuit is
B. 250
C. 2500
D. 25

  ... Answer is (C)



7. Power absorbed in a pure inductive circuit is zero because

A. power factor of the circuit is zero
B. reactive and active components of current cancel out

reactive component of current is zero.
D. active component of current is maximum

... Answer is (A)


8. An alternating voltage v = Vm sin 0 is applied to a pure capacitive circuit. The current equation will be
A. Iₘ sinθ
Iₘ sin (θ - π/2)
C. Iₘ sin (θ + π/4)
D. Iₘ sin (θ + π/2)

... Answer is (D)


9. A 500 V sine wave generator appears across a 10 kΩ resistor. What is the instantaneous current in the resistor at a phase angle of 35°?

A. 52
B. 12.4
C. 22.6
D. 40.6
  ... Answer is (D)


10.  An electric bulb rated at 220 V is connected to 220 V, 5 Hz a.c. source. Then the bulb

glows continuously
B. glows intermittently

does not glow
D. fuses

  ... Answer is (B)



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