D.C. Generators MCQ Questions & Answers

21

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

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Answer & Solution

Answer: Option B

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22

In D.C. generators the pole shoes are fastened to the pole core by

A) Rivets B) Counter sunk screws C) Brazing D) Welding

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Answer & Solution

Answer: Option B

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23

Which generator would you prefer for feeding long D.C. transmission lines?

A) Series generator B) Shunt generator C) Over compound generator D) Flat compound generator

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Answer & Solution

Answer: Option C

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24

In D.C. generators, lap winding is used for

A) High voltage, high current B) Low voltage, high current C) High voltage, low current D) Low voltage, low current

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Answer & Solution

Answer: Option B

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25

Copper brushes in D.C. machine are used

A) Where low voltage and high currents are involved B) Where high voltage and small currents are involved C) In both of the above cases D) In none of the above cases

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Answer & Solution

Answer: Option A

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26

A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly

A) 150 V B) 175 V C) 240 V D) 290 V

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Answer & Solution

Answer: Option C

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27

For both lap and wave windings, there are as many commutator bars as the number of

A) Slots B) Armature conductors C) Winding elements D) Poles

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Answer & Solution

Answer: Option C

Solution:

Commutator bars: In both lap and wave windings of a DC generator, the number of commutator bars is equal to the number of armature conductors.

Reason: Each armature conductor is connected to a commutator bar, and the commutator ensures the reversal of current direction as the armature rotates. This reversal is necessary for maintaining unidirectional current output in the external circuit.

Lap winding: In lap winding, the number of commutator bars is the same as the number of armature coils, which corresponds to the number of armature conductors.

Wave winding: Similarly, in wave winding, the number of commutator bars also equals the number of armature conductors, ensuring proper commutation for each conductor.

Thus, the correct relationship is that the number of commutator bars equals the number of armature conductors.

28

Armature reaction of an unsaturated D.C. machine is

A) Cross-magnetizing B) Demagnetizing C) Magnetizing D) None of above

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Answer & Solution

Answer: Option A

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29

Two generators A and B have 6 poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be

A) 2 : 3 B) 3 : 1 C) 3 : 2 D) 1 : 3

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Answer & Solution

Answer: Option B

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30

A shunt generator can self-excite

A) Only if the resistance of the field circuit is less than critical value B) Only if the resistance of the field circuit is greater than critical value C) Irrespective of the value of the resistance in the field circuit D) None of the above

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Answer & Solution

Answer: Option A

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D.C. Generators MCQ Questions & Answers | Electrical Engineering