DC Generator MCQ

61. The field coils of the DC generator are usually made of

1. mica
2. copper
3. cast iron
4. carbon

62. While applying Fleming’s right-hand rule to find the direction of induced e.m.f., the thumb points towards

1. direction of induced e.m.f.
2. direction of flux
3. direction of motion of the conductor if forefinger points in the direction of generated e.m.f.
4. direction of motion of conductor, if forefinger points along the lines of flux

63. In DC generators, the cause of rapid brush wear may be

1. severe sparking
2. rough commutator surface
3. imperfect contact
4. any of the above

64. Which of the following could be the thickness of laminations of a DC machine?

1. 0.005 mm
2. 0.05 mm
3. 0.5 mm
4. 5 mm

65. In lap winding, the number of brushes is always

1. double the number of poles
2. same as the number of poles
3. half the number of poles
4. two

66. Commutation conditions at full-load a large DC machine can be checked by

1. brake test
   
2. swinburne’s test
   
3. Hopkinson’s test
   
4. None of these

67. In a D.C. machine, how are the commutating pole winding connected?

1. In series with the shunt winding
2. Parallel to the shunt winding
3. In series with the armature winding
4. Parallel to the armature winding

68. The number of conductors of the compensating winding in a DC machine

1. is always more than the number of armature conductors per pole
   
2. is always less than the number of armature conductors per pole
   
3. may be less or more than the number of armature conductors per pole
   
4. none of these

69. In a DC generator commutator acts as a

1. Inverter
   
2. Rectifier
   
3. Collector
   
4. Short circuit

70. Inter-poles are used in

1. Lap wound machines
   
2. Wave wound machines
   
3. Both lap and wave wound machines
   
4. None of these