# What will happen if the back EMF of a DC motor vanishes suddenly?

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If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.

## Which part will surely tell that given motor is DC motor and not an AC type?

Commutator will surely tell that given motor is DC motor and not an AC type.

## What will happen to talk if back emf and speed of DC motor is doubled?

4. What will happen to torque if back emf and speed of the DC motor is doubled? Explanation: Torque depends on armature current, so as long as armature current remains constant torque will not change. Speed depends directly with back emf thus, it will definitely become double when back emf is doubled.

## Is back emf AC or DC?

Back EMF can have either a sinusoidal (AC) or a trapezoidal (DC) waveform. The shape of the back EMF is important, as it determines the type of drive current and commutation method that should be used for the motor.

## What is the back emf of a DC motor?

When the armature of the DC motor rotates under the influence of driving torque, the armature of the conductors moves through a magnetic field inducing an emf in them. The induced emf is in the opposite direction to the applied voltage and is known as the back emf.

## Which is not possible cause for running DC motor slowly?

Explanation: The torque limit of the shunt motor remains constant till the base speed. Explanation: Due to the wrong usage of the fuse wire, it could not sustain the current and in few seconds it was blown off. Explanation: The runaway in large machine is avoided by using compensating winding.

## What happens if DC motor is connected to AC supply?

As the motor is DC so the field and armature winding made for DC supply. The winding which is made for DC always has more resistance than the winding which is made for AC. … For this reason, the motor will be run in very less speed on AC supply. When DC motor Runs on AC supply more loss and heat will occur in the motor.