Competitive Exams: Electronics MCQs (Practice-Test 5 of 13)

  1. The crawling in an induction motor is caused by

    1. improper design of the machine

    2. low voltage supply

    3. high loads

    4. harmonics developed in the motor

    Answer: d

  2. The speed of an induction motor

    1. decreases too much with the increase of load

    2. increase with the increase of load

    3. decreases slightly with the increase of load

    4. remains constant with the increase of load

    Answer: c

  3. The effect of increasing the length of the air gap in an induction motor will increase

    1. power factor

    2. speed

    3. magnetising current

    4. air-gap flux

    Answer: c

  4. the difference between the synchronous speed and the actual speed of an induction motor is known as

    1. Regulation

    2. back lash

    3. slip

    4. lag

    Answer: c

  5. Rotating magnetic field is produced in a

    1. single-phase induction motor

    2. three phase induction motor

    3. dc series motor

    4. ac series motor

    Answer: b

  6. The stator core of the induction motor is made of

    1. Laminated cast iron

    2. Mild steel

    3. Silicon steel stampings

    4. Soft wood

    Answer: c

  7. Star-delta starter of an induction motor

    1. Inserts resistance in rotor circuit

    2. Inserts resistance in stator circuit

    3. Applies reduced voltage to rotor

    4. Applies reduced voltage to stator

    Answer: d

  8. The starting torque of a 1-phase induction motor is

    1. High

    2. Medium

    3. Low

    4. Zero

    Answer: d

  9. The thrust developed by a linear induction motor depends on

    1. Synchronous speed

    2. Rotor input

    3. Number of poles

    4. both A and B

    Answer: d

  10. A 3-phase squirrel cage induction motor supplied from a balanced 3-phase source drives a mechanical load.

    The torque-speed characteristics of the motor (solid curve) and of the load (dotted curve) are shown. Of the two equilibrium points A and B, which of the following options correctly describes the stability of A and B? [GATE 2009]

    1. A is stable B is unstable

    2. A is unstable B is stable

    3. Both are stable

    4. Both are unstable

    Answer: b