Power Generator

21. A transformer is an efficient device because it

1. is a static device
2. uses capacitive coupling
3. uses inductive coupling
4. uses electric coupling

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22. A transformer is so designed that primary and secondary windings have

1. loose magnetic coupling
2. tight magnetic coupling
3. critical magnetic coupling
4. good electric coupling

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23. A transformer operates poorly at very low frequcnies because

1. permeability of core is increased
2. magnetizing current is abnormally high
3. primary reactance is too much
4. permeability core is reduced

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24. A transformer will have zero efficiency at

1. full load
2. half full load
3. no load
4. twice the load

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25. A transformer will work on

1. ac only
2. ac as well as dc
3. dc only
4. pulsating dc

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26. A triplex wave winding will have ___________ parallel paths

1. 6
2. 4
3. 2
4. 8

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27. A type of secondary cell that can be recharged but with an electrolyte that cannot be refilled

1. Sealed rechargeable cell
2. Sealed secondary cell
3. Lealanche cell
4. Alkaline cell

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28. AC machine in which the torque is produced by the interaction of currents in the stator and currents induced in the motor by transformer action

1. squirrel cage motor
2. stepper motor
3. synchronous motor
4. induction motor

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29. After a shunt motor is up to speed the speed may ne increased considerably by

1. increasing field circuit resistance
2. decreasing field circuit resistance
3. increasing the armature circuit resistance
4. reducing the load

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30. An 8 pole duplex lap winding will have ___________ parallel paths

1. 8
2. 32
3. 4
4. 16

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