| 1. | In an induction motor the relationship between stator slots and rotor slots is that ? | |
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stator slots are equal to rotor slots
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stator slots are exact multiple of rotor slots
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stator slots are not exact multiple of rotor slots
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none of the above
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Report Question| 2. | Which motor is preferred for use in mines where explosive gases exist ? | |
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Air motor
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Induction motor
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D.C. shunt motor
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Synchronous motor
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| 3. | If the rotor circuit of a squirrel cage induction motor is open, the rotor will ? | |
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run at very high speed
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run at very low speed
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make noise
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not run
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| 4. | The power factor of an induction motor under no-load conditions is about ? | |
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0.2 lag
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0.4 lag
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unity
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0.4 lead
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| 5. | In an induction motor, the rotor reactance per phase is proportional to ? | |
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s
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1/s
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1/s2
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s2
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| 6. | Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor ? | |
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By changing the number of stator poles
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Rotor rheostat control
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By operating two motors in cascade
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By injecting e.m.f. in the rotor circuit
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| 7. | In case the air gap in an induction motor is increased ? | |
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the magnetising current of the rotor will decrease
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the power factor will decrease
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speed of motor will increase
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the windage losses will increase
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| 8. | A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will be ? | |
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200 Hz
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60 Hz
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2 Hz
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0.2 Hz
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| 9. | The shaft of an induction motor is made of ? | |
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stiff
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flexible
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hollow
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any of the above
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| 10. | In medium sized induction motors, the slip is generally around ? | |
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0.04%
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0.4%
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4%
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14%
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