Electrical Machines
Short circuiting is caused in the armature winding due to

  failure of insulation between two turns of coil.
  grounding of two or more turns of the same coil.
  any of above.
 failure of insulation between two commutator bars.

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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 same as long as the flux density in the air gap remains the same.
 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 more with wave winding than with lap winding.

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