# Induction Machines - Electrical Engineering (MCQ) questions and answers

1)   The NO contact and NC contact of D.O.L. starter is normally

a. Open, closed
b. Closed, open
c. Open, open
d. Closed, closed
 Answer  Explanation ANSWER: Open, closed Explanation: No explanation is available for this question!

2)   In washing machines, most commonly used motors are

a. Split phase induction motors
b. Slip ring induction motors
c. Capacitor start induction motors
 Answer  Explanation ANSWER: Split phase induction motors Explanation: No explanation is available for this question!

3)   For a three phase induction motor, the two rotor frequencies are given by

a. sf, (1 - s) f
b. sf, (2 - s) f
c. (1 - s) f, (2 - s) f
d. Sf , sf
 Answer  Explanation ANSWER: sf, (2 - s) f Explanation: No explanation is available for this question!

4)   A 3 phase induction motor in a short circuit current is equal 3 times of the full load current. If the full load slip is 2%, then the starting torque as a percentage of full load torque is

a. 6% of full load torque
b. 18% of full load torque
c. 36% of full load torque
d. None of these

5)   In terms of slip, the actual speed (N) of the induction motor can be expressed as

a. Ns (1-s)
b. Ns (s-1)
c. Ns / (1-s)
d. Ns / (s-1)
 Answer  Explanation ANSWER: Ns (s-1) Explanation: No explanation is available for this question!

6)   A 50 Hz, 3 phase induction motor with 4 pole stator is supplied by mains, which contains a pronounced fifth time harmonic. The speed of the fifth space harmonic will be

a. 100 rpm
b. 300 rpm
c. 600 rpm
d. 7500
 Answer  Explanation ANSWER: 300 rpm Explanation: No explanation is available for this question!

7)   For moment of inertia to be small in two phase servomotor, the ratio of rotor diameter to its length should be

a. Equal to 1
b. small
c. large
d. All of these
 Answer  Explanation ANSWER: small Explanation: No explanation is available for this question!

8)   A two phase servomotor is commonly used in feedback control system to drive the loads and as sensors to measure

a. Speed of controlled element
b. Position of controlled element
c. Both (a) and (b)
d. None of these
 Answer  Explanation ANSWER: Both (a) and (b) Explanation: No explanation is available for this question!

9)   The flux under the unshaded pole of shaded pole induction motor

a. Is in equal phase of flux under the shaded pole
b. Lags the flux under the shaded pole