Electrical Machines
In a DC machine the armature mmf is

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

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Electrical Machines
Cogging and crawling are phenomena associated with

 cage induction machines and they are essentially the same.
 any of the above.
 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.

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