Electrical Engineering XYZ MCQs
If the back EMF in DC motor vanishes suddenly the motor will:
- Run at very low speed
- Start haunting
- Run at very high speed
- Burn
Correct answer: 4. Burn
Explanation: In a DC motor, back EMF is generated as the motor spins and opposes the applied voltage, effectively reducing the net voltage across the motor’s armature. If the back EMF vanishes suddenly (which might occur if the motor’s speed suddenly drops to zero), the armature would experience the full supply voltage. This leads to a large increase in current through the armature (since V = IR, where V increases while R remains constant). This excessive current can cause the motor to overheat and potentially burn out, due to excessive thermal stress on the motor components.