Objective Type Question or MCQ of D.C Generators page-4

31. For reducing the hysteresis loss in a dc generator

A) armature core material should have high hysteresis coefficient
B) armature core material should have low hysteresis coefficient
C) stator should be laminated
D) armature core should be laminated.

Ans : (B)

32. For a shunt generator, which loss is considered as variable ?

A) Eddy current loss
B) Hysteresis loss
C) Copper loss
D) All of the above.

And : (C)

33. Maximum power output is given by a machine at an efficiency of

A) 75 %
B) 50 %
C) 25 %
D) 0 %.

Ans : (B)

34. Which loss will increase rapidly as compared to others when the number of magnetic reversals is increased ?

A) Eddy current loss
B) Hysteresis loss
C) Copper loss
D) Friction loss.

Ans : (A)

35. A properly designed dc generator can have an overall efficiency of

A) 65 %
B) 85 %
C) 95 %
D) 99 %.

Ans : (C)

36. Out of the following losses in a dc generator, which one has the least proportion ?

A) Windage losses
B) Eddy current losses
C) Hysteresis losses
D) Copper losses.

Ans : (A)

37. In a 10 pole, lap wound dc generator, the number of active armature conductors per pole is 50. The number of compensating conductors per pole required is

A) 100
B) 50
C) 10
D) 5.

Ans : (D)

38. Maximum efficiency in machines occurs when

A) constant losses = variable losses
B) constant losses = losses proportional to square of the current
C) core gets fully saturated
D) machine is running at no load.

Ans : (B)

39. If yf is the front pitch, yb is the back pitch, yc is the commutator pitch, then in wave winding

A) yf + yb = yc
B) yf - yb = yc
C) yb - yf = yc
D) yf + yb = 2yc.

Ans : (D)

40. A sinusoidal voltage of frequency 1 Hz is applied to the field of a dc generator. The armature voltage will be

A) 1 Hz square wave
B) 1 Hz sinusoidal
C) zero
D) non-pulsating dc voltage of rms value unity.

Ans : (B)

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