DC Motors
What will happen if the back emf of a dc motor vanishes suddenly?

The motor will stop
The motor will run noisy
The motor will continue to run
The armature may burn

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DC Motors
The speed of a dc motor is

Directly proportional to flux per pole
None of the listed here
inversely proportional to applied voltage
inversely proportional to flux per pole

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DC Motors
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens

Motor will run at very slow speed
Nothing will happen to the motor
This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
This will make armature to take heavy current, possibly burning it

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