D.C. Machines

61. 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

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62. The direction of rotation of a synchronous motor can be reversed by reversing

1. Current to the field winding
2. Supply phase sequence
3. Polarity of rotor poles
4. None of the above

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63. The drive motor used in a mixer-grinder is a

1. dc motor.
2. induction motor.
3. synchronous motor.
4. universal motor.

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64. The Eb/V ratio of a dc motor is an indication of its

1. Efficiency
2. Speed regulation
3. Starting torque
4. Running Torque

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65. 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

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66. The emf induced in the primary of a transformer

1. is in phase with the flux.
2. lags behind the flux by 90 degree.
3. leads the flux by 90 degree.
4. is in phase opposition to that of flux.

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67. The essential condition for stable parallel operation of two dc generators having similar characteristics is that they should have

1. same kilowatt output ratings
2. dropping voltage characteristics
3. same percentage regulation
4. same no load and full load speed

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68. The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about

1. 50 Hz.
2. 20 Hz.
3. 2 Hz.
4. Zero.

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69. The generation voltage in India is usually

1. between 11 KV and 33 KV.
2. between 132 KV and 400 KV.
3. between 400 KV and 700 KV.
4. None of the above.

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70. The generation voltage is usually

1. between 11 KV and 33 KV.
2. between 132 KV and 400 KV.
3. between 400 KV and 700 KV.
4. None of the above.

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