DC Motors
In a dc machines the residual magnetism is of the order of

10 to 15 percent
20 to 25 percent
50 to 75 percent
2 to 3 percent

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DC Motors
In variable speed motor

Same commutating field is needed at low speed than at high speed
A weaker commutating field is needed at low speed than at high speed
None of these
A stronger commutating field is needed at low speed than at high speed

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