Electrical Engineering Mcqs Practice Test

Question 1

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will__________?

Accepted Answer

A. stop

Question 2

A synchronous machine with low value of short-circuit ratio has___________?

Accepted Answer

A. lower stability limit

Question 3

The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as___________?

Accepted Answer

B. pull-in torque

Question 4

The construction of a synchronous motor resembles____________?

Accepted Answer

C. an alternator

Question 5

For power factor correction, synchronous motors operate at____________?

Accepted Answer

A. no-load and greatly over-excited fields

Question 6

Which of the following losses is not dissipated by the stator core surface in a synchronous motor?

Accepted Answer

D. Windage losses

Question 7

The size of a synchronous motor decreases with the increase in___________?

Accepted Answer

A. flux density

Question 8

Which of the following losses, in a synchronous motor, does not vary with load?

Accepted Answer

A. Windage loss

Question 9

In a synchronous motor, the armature current has large values for____________?

Accepted Answer

C. both high and low excitation

Question 10

The back e.m.f. in the stator of a synchronous motor depends on____________?

Accepted Answer

D. rotor excitation

Question 11

If the field of a synchronous motor is underexcited, the power factor will be_____________?

Accepted Answer

C. lagging

Question 12

In a synchronous motor, the damping winding is generally used to______________?

Accepted Answer

D. prevent hunting and provide the starting torque

Question 13

In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then

Accepted Answer

D. the excitation is said to be hundred per cent

Question 14

In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be____________?

Accepted Answer

B. 1500 r.p.m.

Question 15

In a synchronous motor, V-curves represent relation between____________?

Accepted Answer

A. armature current and field current

Question 16

By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?

Accepted Answer

A. By changing the supply frequency

Question 17

The torque angle, in a synchronous motor, is the angle between_______________?

Accepted Answer

C. the rotating stator flux and rotor poles

Question 18

A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed

Accepted Answer

B. the motor continue to run in the same direction

Question 19

The net armature voltage of a synchronous motor is equal to the_______________?

Accepted Answer

D. vector difference of Eh and V

Question 20

In a synchronous motor, damper windings are provided on____________?

Accepted Answer

C. pole faces