Question: An induction motor with 1000 r.p.m. speed will have____________?

• 1. 8 poles
• 2. 6 poles
• 3. 4 poles
• 4. 2 poles

Question: The term ‘cogging’ is associated with___________?

• 1. three phase transformers
• 2. compound generators
• 3. DC series motors
• 4. induction motors

Question: The number of slip rings on a squirrel cage induction motor is usually____________?

• 1. two
• 2. three
• 3. four
• 4. none

Question: The efficiency of an induction motor can be expected to be nearly____________?

• 1. 60 to 90%
• 2. 80 to 90%
• 3. 95 to 98%
• 4. 99%

Question: A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will be____________?

• 1. 200 Hz
• 2. 50 Hz
• 3. 2 Hz
• 4. 0.2 Hz

Question: In case the air gap in an induction motor is increased?

• 1. the magnetising current of the rotor will decrease
• 2. the power factor will decrease
• 3. speed of motor will increase
• 4. the windage losses will increase

Question: In an induction motor, no-load the slip is generally____________?

• 1. less than 1%
• 2. 1.5%
• 3. 2%
• 4. 4%

Question: The shaft of an induction motor is made of_____________?

• 1. high speed steel
• 2. stainless steel
• 3. carbon steel
• 4. cast iron

Question: The torque of an induction motor is___________?

• 1. directly proportional to slip
• 2. inversely proportional to slip
• 3. proportional to the square of the slip
• 4. none of the above

Question: The frame of an induction motor is usually made of____________?

• 1. silicon steel
• 2. cast iron
• 3. aluminium
• 4. bronze