Electrical Machines
A synchronous generator is feeding a zero power factor (lagging) load at rated current. The armature reaction is

 cross – magnetizing.
 magnetizing.
  demagnetizing.
 ineffective.

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Electrical Machines
Commutation in a DC machine may be explained as a process

  in which magnetic field is set up.
 how alternate flux affects the main field flux.
  by which electric current in a coil is reversed.
 by virtue of which emf is induced in the armature conductors.

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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
Cogging and crawling are phenomena associated with

 the former during starting and the latter at a fraction of its rated speed.
 the former at a fraction of its rate speed and the latter during starting.
 cage induction machines and they are essentially the same.
 any of the above.

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