DC Motors
The greatest percentage of power loss in a dc motor is due to

Copper loss
Windage loss
Friction loss
Core loss

ANSWER DOWNLOAD EXAMIANS APP

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

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

ANSWER DOWNLOAD EXAMIANS APP