Electrical Engineering Mcqs Practice Test

Question 1

In a 3-phase synchronous motor, the negative phase sequence exists when the motor is_______________?

Accepted Answer

A. supplied with unbalanced voltage

Question 2

Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

Accepted Answer

D. Low field current

Question 3

A rotory converter can also be run as a___________?

Accepted Answer

E. synchronous motor

Question 4

In which of the following motors the stator and rotor fields rotate simultaneously?

Accepted Answer

D. Synchronous motor

Question 5

If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then

Accepted Answer

B. the motor stops

Question 6

A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because

Accepted Answer

D. Er (net resultant voltage) in armature is increased

Question 7

If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor

Accepted Answer

B. will become less

Question 8

Stability of a synchronous machine:

Accepted Answer

B. increases with increase in its excitation

Question 9

If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to____________?

Accepted Answer

A. increase in both armature current and power factor angle

Question 10

While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerating torque is produced by_____________?

Accepted Answer

E. all of the above methods

Question 11

A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will___________?

Accepted Answer

C. improve

Question 12

Which of the following motors will be used in electric clocks?

Accepted Answer

D. A.C. synchronous motor

Question 13

Power factor of a synchronous motor is unity when_____________?

Accepted Answer

B. the armature current is minimum

Question 14

Which of the following methods is used to start a synchronous motor?

Accepted Answer

C. Damper winding in conjunction with star-delta starter

Question 15

In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately

Accepted Answer

C. thrice

Question 16

A synchronous machine with large air gap has______________?

Accepted Answer

D. all of the above

Question 17

To limit the operating temperature an electrical machine should have proper____________?

Accepted Answer

B. current rating

Question 18

When the voltage applied to a synchronous motor is increased, which of the following will reduce?

Accepted Answer

D. None of the above

Question 19

Slip rings are usually made of__________?

Accepted Answer

B. brass or steel

Question 20

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

Accepted Answer

B. stator supply is not required to produce magnetic field