D.c. Generators

1. A D.C. generator works on the principle of

Lenz's law
Ohm's law
generator works on the principle of A. Lenz's law B. Ohm's law C. Faraday's law of electromagnetic induction
None of the above

Detailed SolutionA D.C. generator works on the principle of

2. Magnetic field in a D.C. generator is produced by

Electromagnets
Permanent magnets
generator is produced by A. Electromagnets B. Permanent magnets C. Both (A) and (B)
None of the above

Detailed SolutionMagnetic field in a D.C. generator is produced by

3. An exciter for a turbo generator is a

Separately excited generator
Shunt generator
Series generator
Compound generator

Detailed SolutionAn exciter for a turbo generator is a

4. In a D.C. generator the critical resistance refers to the resistance of

Brushes
Field
generator the critical resistance refers to the resistance of A. Brushes B. Field C. Armature
Load

Detailed SolutionIn a D.C. generator the critical resistance refers to the resistance of

5. In D.C. generators, the cause of rapid brush wear may be

Severe sparking
Rough commutator surface
generators, the cause of rapid brush wear may be A. Severe sparking B. Rough commutator surface C. Imperfect contact
Any of the above

Detailed SolutionIn D.C. generators, the cause of rapid brush wear may be

6. A series generator can self-excite

Only if the load current is zero
Only if the load current is not zero
Irrespective of the value of load current
None of the above

Detailed SolutionA series generator can self-excite

7. The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is

2
4
generator having duplex lap winding is A. 2 B. 4 C. 6
8

Detailed SolutionThe number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is

8. A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be

Zero
About 2 V
generator is run at full speed without any excitation. The open circuit voltage will be A. Zero B. About 2 V C. About 50 V
220 V

Detailed SolutionA 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be

9. Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.

Series field
Compensating field
machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure. A. Series field B. Compensating field C. Inter pole field
Shunt field

Detailed SolutionFollowing energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.

10. A separately excited generator as compared to a self-excited generator

Is amenable to better voltage control
Is more stable
Has exciting current independent of load current
Has all above features

Detailed SolutionA separately excited generator as compared to a self-excited generator

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