Electrical Machines
The magnetic field which initially induces emf in the armature in a self excited DC generator is because of

  permanent magnets.
  residual magnetism.
None of these
 armature reaction.

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Electrical Machines
In a DC machine

 current and emf in armature are unidirectional
 emf in armature conductors and at the terminals is alternating.
 current and emf at the terminals are alternating.
 current and emf in armature are alternating.

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