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d c generators MCQs

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

d c generators Mcqs
1. In a D.C. generator the critical resistance can be increased by_____________?
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A. decreasing its speed

B. increasing its field resistance

C. increasing its speed

D. decreasing its field resistance

2. The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage____________?
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A. may be greater or less than 250 V

B. will be less than 250 V

C. will always be 250 V

D. none of the above

3. The series field of a short-shunt D.C. generator is excited by_______________?
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A. armature current

B. shunt current

C. external current

D. load current
4. Which generator would you prefer for feeding long D.C. transmission lines ?
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A. Flat compound generator

B. Over compound generator

C. Shunt generator

D. Series generator

5. If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by______________?
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A. Blv

B. Blv2

C. Bl2v2

D. Bl2v

6. The purpose of providing dummy coils in a generator is__________________?
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A. to reduce eddy current losses

B. to provide mechanical balance for the rotor

C. to amplify voltage

D. to enhance flux density

7. For the parallel operation of two or more D.C. compound generators, we should ensure that_______________?
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A. polarity of incoming generator should be same as that of bus bar

B. series fields of all generators should be either on positive side or negative side of the armature

C. all the series fields should be run in parallel by means of equilizer connection

D. all conditions mentioned above should be satisfied

E. voltage of the incoming generator should be same as that of bus bar

8. Magnetic field in a D.C. generator is produced by_______________?
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A. electromagnets

B. permanent magnets

C. both A. and B.

D. none of the above

9. D.C. generator generally preferred for charging automobile batteries is______________?
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A. any ofthe above

B. series generator

C. shunt generator

D. long shunt compound generator
10. Satisfactory commutation of D.C. machines requires______________?
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A. brushes should be of proper grade and size

B. smooth, concentric commutator properly undercut

C. brushes should smoothly run in the holders

D. all of the above
11. Wave winding is composed of_______________?
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A. that even number which is exact multiple of poles

B. any odd number of conductors

C. any even number of conductors

D. that even number which is exact multiple of poles + 2
12. The field coils of D.C. generator are usually made of_____________?
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A. mica

B. carbon

C. copper

D. cast iron

13. In a D.C. machine stray loss is the sum of_____________?
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A. armature copper loss and iron loss

B. total copper loss and mechanical loss

C. shunt field copper loss and mechanical loss

D. iron loss and mechanical loss
14. The resistance of armature winding depends on
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A. length of conductor

B. number of conductors

C. all of the above

D. cross-sectional area of the conductor

15. In the case of lap winding resultant pitch is____________?
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A. division of front pitch by back pitch

B. difference of front and back pitches

C. multiplication of front and back pitches

D. sum of front and back pitches

16. Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?
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A. Commutator

B. Dummy coils

C. Eye bolt

D. Equilizer rings

17. In D.C. generators the pole shoes are fastened to the pole core by_____________?
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A. rivets

B. welding

C. brazing

D. counter sunk screws
18. Compensating windings are used in D.C. generators______________?
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A. to neutralise the cross-magnetising effect of the armature reaction

B. none of the above

C. to provide path for the circulation of cooling air

D. mainly to reduce the eddy currents by providing local short-circuits

19. D.C. series generator is used_________________?
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A. to supply industrial load at constant voltage

B. to supply traction load

C. voltage at the toad end of the feeder

D. for none of the above purpose

20. In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except______________?
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A. compensating winding

B. shifting of axis of brushes

C. dummy coils

D. interpoles