Alternators MCQs

Question 1

When an alternator is supplying unity power factor load, the armature reaction will produce

Accepted Answer

distortion of the main field

Answer

magnetisation of the main field

Answer

demagnetisation of the main field

Answer

none of the above

Question 2

If the driving force of both the alternators running in parallel is changed, this will result in change in

Accepted Answer

frequency

Answer

generated voltage

Answer

back e.m.f.

Answer

all of the above

Question 3

In an alternator, when the load power factor is unity

Accepted Answer

the armature flux will be cross magnetising

Answer

the armature flux will be damagnetising

Answer

the armature flux will reduce to zero

Answer

the armature flux will have square wave form

Question 4

The Potier's triangle separates the

Accepted Answer

armature leakage reactance and armature reaction m.m.f.

Answer

stator voltage and rotor voltage

Answer

field m.m.f. and armature m.m.f.

Answer

iron losses and copper losses

Question 5

In an alternator zero power factor method is used to find the

Accepted Answer

voltage regulation

Answer

synchronous impedance

Answer

efficiency

Answer

armature resistance

Question 6

If the driving power from the primemover driving an alternator is lost but the alternator remains connected to the supply network and field supply is on, then the alternator will

Accepted Answer

behave as a synchronous motor and will rotate in the same direction

Answer

behave as an induction motor but will rotate an opposite direction

Answer

get burnt

Answer

none of the above

Question 7

In turbo-alternators, smooth cylindrical type rotors used have long axial length because

Accepted Answer

number of armature conductors being less, they have to be necessarily long for generating the required voltage

Answer

it gives smooth running of the rotor

Answer

it reduces windage loss

Answer

centrifugal force is reduced

Question 8

Large-diameter salient-pole rotors have short axial length mainly because

Accepted Answer

number of armature conductors held in the large circuimference rotor being very large, they need not be long

Answer

it occupies much less space

Answer

it reduces rotor weight

Answer

it save lot of copper in stator winding

Question 9

At leading power factor, the armature flux in an alternator

Accepted Answer

aids the rotor flux

Answer

distorts the rotor flux

Answer

opposes the rotor flux

Answer

does not affect the rotor flux