D.C. Generators

41. In a D.C. generator the critical resistance can be increased by

  1. increasing its field resistance
  2. decreasing its field resistance
  3. increasing its speed
  4. decreasing its speed

Correct answer: (C)
increasing its speed

42. In a D.C. generator the critical resistance refers to the resistance of

  1. brushes
  2. field
  3. armature
  4. load

Correct answer: (B)
field

43. In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when

  1. there is no load on|he generator
  2. the generator runs on full load
  3. the generator runs on overload
  4. the generator runs on designed speed

Correct answer: (A)
there is no load on|he generator

44. In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when

  1. r.p.m. is more than 300
  2. r.p.m. is less than 300
  3. number of poles is 4
  4. number of poles is 2

Correct answer: (D)
number of poles is 2

45. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by

  1. using conductor of annealed copper
  2. using commutator with large number of segments
  3. using carbon brushes of superior quality
  4. using equiliser rings

Correct answer: (C)
using carbon brushes of superior quality

46. In a D.C. machine stray loss is the sum of

  1. total copper loss and mechanical loss
  2. armature copper loss and iron loss
  3. shunt field copper loss and mechanical loss
  4. iron loss and mechanical loss

Correct answer: (C)
shunt field copper loss and mechanical loss

47. In a four-pole D.C. machine

  1. all the four poles are north poles
  2. alternate poles are north and south
  3. all the four poles are south poles
  4. two north poles follow two south poles

Correct answer: (B)
alternate poles are north and south

48. In a level compounded D.C. generator, full load terminal voltage is

  1. negligibly low
  2. equal to no-load terminal voltage
  3. more than no-load terminal voltage
  4. less than no-load terminal voltage

Correct answer: (B)
equal to no-load terminal voltage

49. In a separately excited generator supplying rated load the armature reaction ,

  1. is always present
  2. is always absent
  3. may be sometimes present
  4. none of the above

Correct answer: (A)
is always present

50. In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called

  1. rotor
  2. stator
  3. field
  4. armature

Correct answer: (D)
armature

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