Question: Slip rings are usually made of___________?

• 1. copper
• 2. carbon
• 3. phospor bronze
• 4. aluminium

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 squirrel cage induction motors, the rotor slots are usually given slight skew in order to__________?

• 1. reduce windage losses
• 2. reduce eddy currents
• 3. reduce accumulation of dirt and dust
• 4. reduce magnetic hum

Question: In medium sized induction motors, the slip is generally around___________?

• 1. 0.04%
• 2. 0.4%
• 3. 4%
• 4. 14%

Question: Which of the following component is usually fabricated out of silicon steel ?

• 1. Bearings
• 2. Shaft
• 3. Statorcore
• 4. None of the above

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