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A dc series motor must never be started on no load because

  • A.its speed would rise to a destructive value
  • B.its armature current would become excessive
  • C.its field winding would overheat immediately
  • D.its commutator would fail to make contact

Answer: A

With little current there is little flux, and the speed must rise enormously before the back emf can balance the supply. Such machines are geared or coupled directly to their load rather than driven through a belt that could break.

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