Electrical Machines
In a 3 - Φ IM in order to eliminate cogging the number of stator slots must be

  an integral multiple of number of rotor slots.
  equal to number of rotor slots.
  either (B) or (C).
  unequal to number of rotor slots and skewed in shape.

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Electrical Machines
Flashing of DC generator means

None of these
  increasing flux density by providing extra ampere-turns in field.
  creation of residual magnetism by a DC source.
 neutralization of residual magnetism.

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