Electrical Machines
A 4 pole wave wound dc motor having flux per pole of 9.56 X 10-3 Wb contains 460 armature conductors. Calculate the back emf produced when it is running at a speed of 1500 rpm.

 230 volt.
 240 volt.
  220 volt.
 440 volt.

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

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Electrical Machines
The synchronous motor can be started by

  providing damper winding in its rotor circuit.
  coupling it with a small AC induction motor called the pony motor.
  any of the above methods.
  coupling it with a DC compound motor.

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