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

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

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DC Motors
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens

This will make armature to take heavy current, possibly burning it
This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
Motor will come to stop
Nothing will happen to motor

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