Electrical Machines
Armature reaction in a DC machine

 is in direct opposition to the main poles.
 is in the same direction as the main poles.
  makes an angle of 90° with the main pole axis.
 makes an angle with the main pole axis which is load dependent.

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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.
 4.
 8.
 1/4.

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