MCQOPTIONS

Explore topic-wise MCQs in Electrical Engineering Mcqs.

This section includes 19 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Mcqs knowledge and support exam preparation. Choose a topic below to get started.

1.	Synchronous motors are generally not self-starting because:
A.	The direction of rotation is not fixed
B.	The direction of instantaneous torque reverses after half cycle
C.	Startes cannot be used on these machines
D.	Starting winding is not provided on the machines
Answer» C. Startes cannot be used on these machines

2.	If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
A.	It runs at a slower speed
B.	The motor stops
C.	It continues to run at the same speed
D.	It runs at a very high speed
Answer» C. It continues to run at the same speed

3.	A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
A.	Speed of the motor is reduced
B.	Power factor is decreased
C.	Eb (back e.m.f.) becomes less than V (applied voltage)
D.	Er (net resultant voltage) in armature is increased
Answer» E.

4.	Stability of a synchronous machine:
A.	Decreases with increase in its excitation
B.	Increases with increase in its excitation
C.	Remains unaffected with increase in excitation
D.	Any of the above
Answer» C. Remains unaffected with increase in excitation

5.	As the load is applied to a synchronous motor, the motor takes more armature current because
A.	The increased load has to take more current
B.	The rotor by shifting its phase backward causes motor to take more current
C.	The back e.m.f. decreases causing an increase in motor current
D.	The rotor strengthens the rotating field casuing more motor current
Answer» C. The back e.m.f. decreases causing an increase in motor current

6.	Slip rings are usually made of__________?
A.	Carbon or graphite
B.	Brass or steel
C.	Silver or gold
D.	Copper or aluminium
Answer» C. Silver or gold

7.	Synchronous motors are_____________?
A.	Not-self starting
B.	Self-starting
C.	Essentially self-starting
D.	None of the above
Answer» B. Self-starting

8.	Synchronsizing power of a synchronous machine is_____________?
A.	Direcly proportional to the synchronous reactance
B.	Inversely proportional to the synchronous reactance
C.	Equal to the synchronous reactance
D.	None of the above
Answer» C. Equal to the synchronous reactance

9.	If load (or torque) angle of a 4-pole synchronous motor is 6 electrical, its value in mechanical degrees is__________?
A.	2
B.	3
C.	4
D.	6
Answer» C. 4

10.	Synchronous motor always runs at______________?
A.	The synchronous speed
B.	Less than synchronous speed
C.	More than synchronous speed
D.	None of the above
Answer» B. Less than synchronous speed

11.	Which of the following motors is non-self starting ?
A.	D.C. series motor
B.	Synchronous motor
C.	Squirrel cage induction motor
D.	Wound round induction motor
Answer» C. Squirrel cage induction motor

12.	When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way
A.	Augments it directly
B.	Directly opposes it
C.	Cross-magnetises it
D.	None of the above
Answer» C. Cross-magnetises it

13.	An important advantage of a synchronous motor over wound round induction motor is that
A.	Its power factor may be varied at will
B.	Its speed is independent of supply frequency
C.	Its speed may be controlled more easily
D.	None of the above
Answer» B. Its speed is independent of supply frequency

14.	Slip-rings in a synchronous motor carry____________?
A.	Direct current
B.	Alternating current
C.	No current
D.	All of the above
Answer» B. Alternating current

15.	The power factor of a synchronous motor is better than that of induction motor because
A.	Stator supply is relieved of responsibility of producing magnetic field
B.	Mechanical load on the motor can be adjusted
C.	Synchronous motor runs at synchronous speed
D.	Synchronous motor has large air gap
Answer» B. Mechanical load on the motor can be adjusted

16.	. In a synchronous motor which loss varies with load ?
A.	Windage loss
B.	Bearing friction loss
C.	Copper loss
D.	Core loss
Answer» D. Core loss

17.	By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?
A.	By changing the supply frequency
B.	By interchanging any two phases
C.	By changing the applied voltage
D.	By changing the load
Answer» B. By interchanging any two phases

18.	Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?
A.	High field current
B.	Low short circuit ratio
C.	High core losses
D.	Low field current
Answer» E.

19.	Which of the following losses, in a synchronous motor, does not vary with load?
A.	Windage loss
B.	Copper losses
C.	Any of the above
D.	None of the above
Answer» B. Copper losses