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Objective questions and answers or MCQ of Electrical Machines page-20


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311. The electric current in the motor generator

a) Heat only
b) Magnetic field only
c) (a) and (b)
d) Power only

Ans: (c)

312. Which of the following machine will be preferred to charge the batteries?

a) Series generator
b) Series motor
c) Shunt generator
d) Compound generator
e) Shunt motor
f) None of the above

Ans: (c)

313. If the speed of a d.c. shunt motor is increased, the back emf of the motor will

a) Decrease
b) Increase
c) Remain same
d) Increase then decrease

Ans: (b)

314. The large number of slots in induction motor

a) Provides better overload capacity
b) Reduces overload capacity
c) Provides bigger size of motor
d) Reduces the size of motor

Ans: (a)

315. The good power factor of an induction motor can be achieved if the average flux density in air gap is

a) Large
b) Small
c) Infinity
d) Absent

Ans: (b)

316. Why the d.c. motors are preferred for traction applications?

a) The torque is proportional to armature current.
b) The torque is proportional to square root of armature current.
c) The speed is inversely proportional to the torque and the torque is proportional to square of armature current.
d) Torque and speed are inversely proportional to armature current.

Ans: (c)

317. Which of the following generating machine will offer constant voltage on all loads?

a) Separately excited generator
b) Self-excited generator
c) Level compound generator
d) All the above machines

Ans: (c)

318. The d.c. generator will be preferred if it has

a) 100% regulation
b) Small
c) 10% regulation
d) Infinity

Ans: (b)

319. The number of bushings in a transformer can be reduced if

a) The tapping are provided at the phase ends
b) The tapping are provided at the high voltage side
c) The tapping are provided in middle of the transformer
d) The tapping are provided on the low voltage side

Ans: (a)

320.Which of the following transformers will use oil natural cooling with tubes?

a) 100 kVA
b) 800 kVA
c) All the above transformers

Ans: (c)

321. An induction motor with 1000 rpm speed will have

a) 2 poles
b) 6 poles
c) 4 poles
d) 8 poles

Ans: (b)

322. Which of the following equipment will draw the reactive power?

a) Electrical iron
b) Tubelight
c) Three phase motor
d) rectifier

Ans: (c)

323. The large number of narrow slots in stator of an a.c. motor is preferred because

a) It is easier to make narrow slots than wide open slots
b) Large number of narrow slots reduces motor noise
c) Large number of narrow slots reduces noise and tooth pulsation losses
d) It helps in uniform distribution of flux

Ans: (c)

324. The number of parallel paths in wave winding of machine is

a) 4
b) 6
c) 2
d) 8

Ans: (c)

325. The alternators are normally designed for the torque angle of the order of

a) 3° to 5°
b) 2 rad to 3 rad
c) 15° to 30°
d) 1° to 3°

Ans: (d)


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