Wednesday, September 9, 2020

Chapter 4: Complex AC Circuits- Page 6

 

Chapter 4: Complex AC Circuits

51. The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing through a given circuit for a given time produces
A. the less heat than produced by A.C. flowing through the same circuit
B. the same heat as produced by A.C. when flowing through the same circuit
C. the more heat than produced by A.C. when flowing through the same circuit
D. None of the above


... Answer is (B)

 

 
 

52. In a loss-free R-L-C circuit the transient current is
 

A. oscillating
B. square wave
C. sinusoidal
D. non-oscillating

... Answer is (C)

 
 
 

53. In the R-L-C containing R = 4.5 ᘯ, L = 0.06 H, C = 0.6 μf the power factor will be

A. leading
B. unity

C.
zero
D. lagging

... Answer is (A)

 

 
 

54. The time constant of the capacitance circuit is defined as the time during which voltage

 
A. rise to 63.2% of its final steady value
B. falls to 36.8% of its final steady value
C. rises to 38.6% of its final steady value
D. none of the above

  ... Answer is (A)

 

 
 
55. Power factor of the system is kept high
  ...
Answer is (D)

 
 
 

56. Power factor of the following circuit will be unity
A.
resistance
B.
inductance
C. capacitance
D. All of the above

  ... Answer is (A)

 

 
 

57. Power factor of the following circuit will be zero
A.
resistance only
B.
capacitance
C. inductance 

D. Both (B) and (C)

... Answer is (D)

 
 

58. In a pure inductive circuit

A. the current leads the voltage by 90°
B. the current canlead or lag by 90°
C.
the current is in phase which the voltage
D. the current lags behind the voltage by 90°

... Answer is (D)

 
 

59. In a pure resistive circuit

A. current can lead or lag the voltage by 90°
B. current is in phase with the voltage
C. current lags behind the voltage by 90°
D. current leads the voltage by 90°
 
  ... Answer is (B)

 
 

60.  In the case of an unsymmetrical alternating current the average value must always be taken over
A.
the half cycle
B. the whole cycle
C. unsymmetrical part of the wave from
D. the quarter cycle

  ... Answer is (B)

 

 

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