MCQ on DC generator 61-80

61. Armature coil is short circuited by brushes when it lies
(a) along neutral axis✔
(b) along field axis
(c) in any of the above positions
(d) in none of the above positions

62. A cumulatively compounded long shunt generator when operating as a motor would be
(a) cumulatively compounded long shunt
(b) differentially compounded long shunt✔
(c) cumulatively compounded short shunt
(d) differentially compounded short shunt

63. To avoid formation of grooves in the commutator of a D.C. machine
(a) the brushes of opposite polarity should track each other✔
(b) the brushes of same polarity should track each other
(c) brush position has no effect on the commutator grooving

64. The following constitute short-circuit in the armature winding.
(a) Insulation failure between two commutator bars
(b) Insulation failure between two turns of a coil
(c) Two of more turns of the same coil getting grounded
(d) All of the above✔

65. The rapid wear of brushes takes place due to
(a) abrasion from dust
(b) excessive spring pressure
(c) rough commutator bars
(d) all of the above factors✔

66. Number of tappings for each equilizer ring is equal to
(a) number of pole pairs✔
(b) number of poles
(c) number of parallel paths
(d) number of commutator segments

67. A D.C. generator can be considered as
(a) rectifier
(b) primemover
(c) rotating amplifier✔
(d) power pump

68. In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called
(a) rotor
(b) stator
(c) field
(d) armature✔

69. In a D.C. machine stray loss is the sum of
(a) total copper loss and mechanical loss
(b) armature copper loss and iron loss
(c) shunt field copper loss and mechanical loss
(d) iron loss and mechanical loss✔

70. Lap winding is composed of
(a) any even number of conductors✔
(b) any odd number of conductors
(c) that even number which is exact multiple of poles + 2
(d) that even number which is exact multiple of poles

71. In a D.C. generator in case the resistance of the field winding is increased, then output voltage will
(a) increase
(b) decrease✔
(c) remain unaffected
(d) fluctuate heavily

72. An exciter for a turbo generator is a
(a) separately excited generator
(b) shunt generator✔
(c) series generator
(d) compound generator

73. In case of a flat compounded generator
(a) voltage generated is less than the rated voltage
(b) generated voltage is proportional to the load on the generator
(c) voltage remains constant irrespective of the load✔
(d) speed varies in proportion to the load on the generator

74. Which of the following generator will have negligible terminal voltage while running on no-load ?
(a) Series generator✔
(b) Shunt generator
(c) Compound generator
(d) Separately excited generator

75. Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ?
(a) Series generator
(b) Shunt generator
(c) Compound generator
(d) None of the above✔

76. In over compounded generator, full load terminal voltage is
(a) almost zero
(b) less than no load terminal voltage
(c) more than no load terminal voltage✔
(d) equal to no-load terminal voltage

77. In a level compounded D.C. generator, full load terminal voltage is
(a) negligibly low
(b) equal to no-load terminal voltage✔
(c) more than no-load terminal voltage
(d) less than no-load terminal voltage

78. The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except
(a) armature reaction
(b) armature resistance drop
(c) field weakening due to armature reaction and armature
(d) commutation✔

79. In a D.C. generator
(a) external resistance = internal char-acteristic – armature reaction
(b) internal characteristic = magnetisation characteristic – ohmic drop
(c) external characteristic = magnetisation characteristic – ohmic drop – armature reaction✔
(d) magnetisation characteristic = external characteristic

80. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave
(a) will be zero
(b) will be of 5 Hz✔
(c) will be of 5 xiVHz
(d) will be of v Hz 5