d c generators MCQs – Page 6

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

d c generators Mcqs
101. 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______________?
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A. increase the field resistance

B. reverse the field connections

C. increase the speed of primemover

D. check armature insulation resistance

102. If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be____________?
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A. the same as rated voltage

B. high

C. zero

D. small

103. The e.m.f. generated in a D.C. generator is directly proportional to____________?
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A. number of poles

B. all of the above

C. speed of armature

D. flux/pole

104. When two D.C. series generators are running in parallel, an equilizer bar is used________________?
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A. to increase the speed and hence generated e.m.f.

B. to increase the series flux

C. so that two similar machines will pass approximately equal currents to the load

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

105. In a D.C. generator the ripples in the direct e.m.f. generated are reduced by_____________?
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A. using conductor of annealed copper

B. using commutator with large number of segments

C. using carbon brushes of superior quality

D. using equiliser rings

106. A D.C. welding generator has____________?
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A. wave moving

B. lap winding

C. any of the above

D. duplex winding

107. Shunt generators are most suited for stable parallel operation because of their______________?
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A. identical voltage characteristics

B. rising voltage characteristics

C. drooping voltage characteristics

D. linear voltage characteristics

108. The armature core of a D.C. generator is usually made of__________________?
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A. copper

B. non-ferrous material

C. cast-iron

D. silicon steel
109. Following D.C. generator will be in a position to build up without any residual magnetism in the poles______________?
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A. series generator

B. shunt generator

C. self-excited generator

D. compound generator

110. Open circuited armature coil of a D.C. machine is________________?
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A. identified by the scarring of the commutator segment to which open circuited coil is connected

B. indicated by a spark completely around the commutator

C. both A. and (b)

D. none of the above

111. The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be_____________?
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A. 640 V

B. 600 V

C. 580 V

D. 620 V

112. With a D.C. generator which of the following regulation is preferred ?
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A. 50% regulation

B. 100% regulation

C. infinite regulation

D. 1% regulation
113. Which of the following generator will have negligible terminal voltage while running on no-load?
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A. Compound generator

B. Shunt generator

C. Series generator

D. Separately excited generator

114. Iron losses in a D.C. machine are independent of variations in______________?
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A. load

B. speed and voltage

C. voltage

D. speed

115. Number of tappings for each equalizer ring is equal to_____________?
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A. number of poles

B. number of parallel paths

C. number of commutator segments

D. number of pole pairs
116. Iron losses in a D.C. machine are independent of variations in_____________?
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A. speed

B. voltage

C. load

D. speed and voltage

117. A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave will_____________?
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A. will be of 5 xiVHz

B. will be of 5 Hz

C. will be of v Hz 5

D. will be zero

118. In a commutator_____________?
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A. mica and copper are equally hard

B. mica is harder than copper

C. none of the above

D. copper is harder than mica

119. A cumulatively compounded long shunt generator when operating as a motor would be____________?
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A. cumulatively compounded short shunt

B. cumulatively compounded long shunt

C. differentially compounded short shunt

D. deferentially compounded long shunt
120. According to Flemings right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of____________?
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A. lines of force

B. either of the above

C. none of the above

D. motion of conductor