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SymbolsTransformerRelayPower-SystemBasic-electricalACSR-ConductorCircuit-BreakerInterview-questions-of-Basic-ElectricityInterview-questions-of-transformerInsulatorCurrent-TransformerMCQMCQ-powersystemThermal-power-stationInterview-questions-of-Power-SystemPower-ElectronicsInterview-questions-of-Underground-CableInterview-questions-of-IlluminationIlluminationMCQ-of-ElectronicsMCQ-of-Basic-ElectricalMCQ-of-Transformers MCQ-of-D.C-motor MCQ-of-D.C-generators

MCQ of D.C generators page-1

1.The operation of an electric motor or generator is based on

a) The law of electromagnetic induction
b) Interaction between magnetic field and current carrying conductor
c) Interaction between two electric fields
d) Interaction between magnetic field and electric field

Ans: (b)

2. All rotating electric machines are basically

a) D.c. machines
b) A.c. machines
c) Electro-mechanical convertors
d) Machines using electromagnetic induction

Ans: (c)

3. All rotation electrical machines have

a) Rotating armature and fixed field
b) Rotating field and fixed armature
c) Either (a) or (b)
d) None of these

Ans: (a)

4. In any dc generators, the emf generated in the armature is maximum when

a) Flux linkage with conductors is maximum
b) Flux linkage with conductors is minimum
c) Rate of change of flux linkage is maximum
d) Rate of change of flux linkage is minimum

Ans: (c)

5. Under commutation in a dc machine gives rise to

a) Sparking at the trailing edge of the brush
b) Sparking at the leading edge of the brush
c) Sparking at the middle of the brush
d) No sparking at all

Ans: (a)

6. The function of commutation in a dc machine is

a) To provide easy speed control
b) To change ac voltage into dc voltage
c) To change dc voltage into dc voltage
d) To improve commutation

Ans: (b)

7. V×B = e is the equation of the electrical machines which

a) Converts mechanical energy into electrical energy
b) Has magnetic poles
c) Works as a motor
d) Is a dc machine

Ans: (a)

8. All dc machines are characterized by

a) Magnetic poles
b) Electric brushes
c) Armature
d) Commutator

Ans: (d)

9. In a dc generator, if the brushes are given a small amount of forward shift, the effect of armature reaction is

a) Totally cross-magnetizing
b) Totally magnetizing
c) Totally demagnetizing
d) Partly demagnetizing and partly cross-magnetizing

Ans: (d)

10. Commutation in a dc machine may be improved by

a) Reducing to number of turns in the armature and segments of commutator
b) Increasing the resistance of brushes
c) Neutralizing the reactance voltage by producing a reverse emf in the coil undergoing commutation
d) All of these

Ans: (d)

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