ELECTRICAL MACHINES QUIZ

Which of the following is/are the advantages of carbon brush over the copper brush?

In case of any sparking they will be less damaged than copper brushes

They are not hard as copper brush

All of these

They are self lubricating in nature

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A DC shunt generator builds up 230 V when driven in clockwise direction. In case it is driven in anti clockwise direction, other things remaining unchanged, then the voltage build up is

some what more than 230 V

230 V

some what less than 230 V

not possible

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In a DC generator the emf generated by the armature is maximum when

induced voltage is high.

rate of change of flux is maximum.

rate of change of flux is minimum.

shaft rotation is high.

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Short circuit test is performed on a transformer with a certain impressed voltage at rated frequency. If the short circuit test is now performed with the same magnitude of impressed voltage, but at frequency higher than the rated frequency then

The magnitude of circuit as well as the power factor will decrease.

The magnetude of current will increase, but power factor will decrease.

The magnitude of current will decrease but the power factor will increase.

The magnitude will both increase.

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In travelling cranes for swing action which motor is preferred?

Capacitor type induction motors.

AC slip ring IM.

Reluctance motor.

DC series motor.

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Maximum power developed depends on

load angle

both 1and 2

reactance

voltage

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In a DC motor under constant terminal voltage what is the relation between torque (Te) and power (P)

T∝ P³

T is independent of P

T∝ P²

T∝ P

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The ___________________ generator has the poorest voltage regulation.

over compounded.

under-compounded.

differential compounded.

shunt.

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Stray losses in transformer occurs in

paper insulation in transformers.

steel core.

transformer insulating oil.

winding conductors and steel structures of transformer.

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Compensating windings is placed in which part of a D.C motor?

On yoke in the inter pole gap.

On yoke in the pole faces.

None of these

On armature.

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