DC Generator Multiple Choice Questions and Answers

61. Eddy currents are induced in the pole shoes of a D.C. machine due to

1. oscillating magnetic field
2. pulsating magnetic flux
3. relative rotation between field and armature
4. all above

62. 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

63. A D.C. generator can be considered as

1. rectifier
2. primemover
3. rotating amplifier
4. power pump

64. The armature of D.C. generator is laminated to

1. reduce the bulk
2. provide the bulk
3. insulate the core
4. reduce eddy current loss

65. The demagnetising component of armature reaction in a D.C. generator

1. reduces generator e.m.f.
2. increases armature speed
3. reduces interpoles flux density
4. results in sparking trouble

66. If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to

1. reverse the field connections
2. increase the field resistance
3. increase the speed of primemover
4. check armature insulation resis¬tance

67. Shunt generators are most suited for stable parallel operation because of their

1. rising voltage characteristics
2. identical voltage characteristics
3. drooping voltage characteristics
4. linear voltage characteristics

68. In D.C. generators the pole shoes are fastened to the pole core by

1. rivets
2. counter sunk screws
3. brazing
4. welding

69. 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

70. In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be

1. 4
2. 8
3. 16
4. 32