DC Motors MCQs

Question 1

Electromagnetic torque and speed are in opposite directions in the case of

Accepted Answer

shunt generators

Answer

shunt motors

Answer

series motors

Answer

all of these

Question 2

The function of a starter in a dc machine is to

Accepted Answer

avoid excessive current at starting

Answer

avoid armature reaction

Answer

control the speed

Answer

avoid excessive heating

Question 3

In dc machines, the armature reaction mmf is.

Accepted Answer

stationary with respect to the stator

Answer

stationary with respect to the armature

Answer

rotating with respect to the stator

Answer

rotating with respect to brushes

Question 4

A cumulatively compound dc generator supplies 15 A at 240 V. No if the series field winding is short circuited, the terminal voltage

Accepted Answer

will reduce below 240 V

Answer

will remain unaltered at 240 V

Answer

will rise to 260 V

Answer

will shoot up to a very high value

Question 5

In a dc machine

Accepted Answer

torque and induced emf are produced both in motor and generator

Answer

torque is produced in motor and emf is induced in generator

Answer

torque is produced in generator and emf is induced in motor

Answer

none of these

Question 6

Function of the interpoles in the dc generators is to

Accepted Answer

neutralize cross magnetizing effects of a armature reaction.

Answer

neutralize the reactance voltage

Answer

make commutation sparkles

Answer

all the above

Question 7

Which of the following is not a cross field machine?

Accepted Answer

Level compound generator with interpoles

Answer

Amplidyne

Answer

Rosenberg dynamo

Answer

Metadyne

Question 8

A d.c. shunt generator has full-load voltage regulation of 10% at rated speed of 1000 r.p.m. If it is now driven at 1250 r.p.m., then its voltage regulation at full load would

Accepted Answer

be more than 10%

Answer

be less than 10%

Answer

remain unchanged

Answer

be 12.5%

Question 9

Load saturation characteristic of a dc generator gives relation between

Accepted Answer

V and la

Answer

V and Ia

Answer

E and Ia

Answer

E0 and If