Electrical Machines
In a DC machine the armature mmf is

  stationary with respect to field poles.
  stationary with respect to armature.
  rotating with respect to field poles as well as armature.
 rotating with respect to field poles.

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Electrical Machines
If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then

 Ph will increase but Pe will decrease
 both hysteresis loss(Ph) and eddy current loss(Pe) will increase
 Ph will decrease but Pe will remain same
 Pe will increase but Ph will decrease

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