Electrical Machines
For a 3-phase, 4 pole, 50 Hz synchronous motor the frequency, pole number and the frequency are halved. The motor speed will be

 1500 rpm
 375 rpm
 75 rpm
 3000 rpm

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Electrical Machines
The compensating winding in a DC machine

  is located on pole shoes for avoiding the flashover at the commutator.
 is located in armature slots for compensation of the armature reaction.
  is located on pole shoes to avoid the sparking at the brushes.
 is located on commutating poles for improving commutation.

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Electrical Machines
Two 3-phase AC generators are such that one has twice the linear dimensions of the other. The field windings of each are excited to give identical sinusoidal air-gap flux density waveform. Both have the same number of stator slots and identical winding patterns. The conductor/slot in a big generator is K times that of the smaller one. The value of K to get equal no load voltage at same frequency is

  1/2.
 1/4.
 4.
 8.

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Electrical Machines
In a 3 - Φ induction motor

  power factor at starting is low as compared to that while running.
  power factor at starting is high as compared to that while running.
  power factor at starting in the same as that while running.
  none of them.

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