Electrical Machines
For 250 volt DC Shunt Motor the armature and field resistance are 0.5 ohm and 250 ohm respectively. What will be the back e.m.f. produced when it takes a load current of 21A.

 220 V.
 280 V.
 240 V.
 150 V.

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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
 Pe will increase but Ph will decrease
 Ph will decrease but Pe will remain same

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Electrical Machines
In a DC machine the armature mmf is

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

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