d c generators MCQs – Page 5

Practise focused d c generators questions with marked answers for exam preparation and subject revision.

d c generators Mcqs
81. If a D.C. generator fails to build up the probable cause could not be_____________?
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A. no residual magnetism in the generator

B. field resistance less than the critical resistance

C. imperfect brush contact

D. faulty shunt connections tending to reduce the residual magnetism

82. Laminations of core are generally made of________________?
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A. stainless steel

B. case iron

C. carbon

D. silicon steel
83. In a D.C. generator the critical resistance refers to the resistance of_____________?
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A. field

B. load

C. brushes

D. armature

84. The critical resistance of the D.C. generator is the resistance of_____________?
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A. field

B. load

C. armature

D. brushes

85. The function of pole shoes in the case of D.C. machine is______________?
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A. to spread out the flux to achieve uniform flux density

B. to support the field coil

C. to discharge all the above functions

D. to reduce the reluctance of the magnetic path

86. In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilized is called____________?
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A. armature

B. stator

C. rotor

D. field

87. Equilizer rings are required in case armature is_______________?
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A. lap wound

B. wave wound

C. delta wound

D. duplex wound

88. A separately excited generator as compared to a self-excited generator_____________?
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A. is amenable to better voltage control

B. is more stable

C. has exciting current independent of load current

D. has all above features
89. When two D.C. generators are running in parallel an equilizer bar is used______________?
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A. to increase the series flux

B. to increase the generated e.m.f.

C. to reduce the combined effect of ar-mature reaction of both the machines

D. so that the two identical machines will pass approximately equal currents to the load
90. In case of a flat compounded generator:
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A. voltage remains constant irrespective of the load

B. speed varies in proportion to the load on the generator

C. voltage generated is less than the rated voltage

D. generated voltage is proportional to the load on the generator

91. The following constitute short-circuit in the armature winding.
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A. Insulation failure between two turns of a coil

B. Insulation failure between two commutator bars

C. All of the above

D. Two of more turns of the same coil getting grounded

92. The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is______________?
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A. 8

B. 2

C. 6

D. 4
93. Permeance is the reciprocal of______________?
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A. ampere-turns

B. reluctance

C. flux density

D. resistance

94. Armature coil is short circuited by brushes when it lies_____________?
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A. along field axis

B. in none of the above positions

C. in any of the above positions

D. along neutral axis
95. In case of D.C. machine winding, number of commutator segments is equal to______________?
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A. number of armature turns

B. number of armature conductors

C. number of armature coil sides

D. number of armature coils
96. In a D.C. generator:___________________?
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A. internal characteristic = magnetisation characteristic ohmic drop

B. magnetisation characteristic = external characteristic

C. external resistance = internal char-acteristic armature reaction

D. external characteristic = magnetisation characteristic ohmic drop armature reaction
97. Which of the following could be lamina-proximately the thickness of laminations of a D.C. machine ?
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A. 0.005 mm

B. 0.05 mm

C. 0.5 m

D. 5 m

98. Armature reaction of an unsaturated D.C. machine is_____________?
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A. crossmagnetising

B. none of above

C. demagnetising

D. magnetising

99. In lap winding, the number of brushes is always_____________?
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A. same as the number of poles

B. double the number of poles

C. two

D. half the number of poles

100. Interpole flux should be sufficient to_____________?
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A. neutralise the commutating self induced e.m.f.

B. neutralise the armature reaction flux

C. neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil

D. perform none of the above functions