Electrical Machines
What is the mechanical power developed by a DC series motor is maximum?

 Back emf is equal to applied voltage.
 Back emf is equal to half the applied voltage.
 Back emf is equal to zero.
 None of above.

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Electrical Machines
The mmf produced by rotor currents of a 3 - Φ induction motor

  rotates at the speed of rotor in the air gap.
  rotates at slip speed with respect to stator mmf.
  is at standstill with respect to stator mmf.
  rotates at synchronous speed with respect to rotor.

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Electrical Machines
In a DC machine, for the same value of φ, Z and N; which one of the following statements is correct?

  Armature emf is more with wave winding than with lap winding.
 Armature emf depends on weather the machine is running as a motor or generator.
 Armature emf is less with wave winding than with lap winding.
 Armature emf is same as long as the flux density in the air gap remains the same.

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Electrical Machines
In a loaded DC generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

 improve with fall of terminal voltage.
 deteriorate with rise in terminal voltage.
 deteriorate with fall of terminal voltage.
 improve with rise in terminal voltage.

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