Back emf is very significant in the working of a dc motor. The presence of back emf makes the d.c. motor a self-regulating machine i.e., it makes the motor to draw as much armature current as is just sufficient to develop the torque required by the load.

## What is the use of back emf in DC motor?

The back emf opposes the supply voltage. The supply voltage induces the current in the coil which rotates the armature. The electrical work required by the motor for causing the current against the back emf is converted into **mechanical energy**. And that energy is induced in the armature of the motor.

## What is back emf of DC motor and what is its function in 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.

## 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 purpose of back emf?

A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. This emf, known as the back emf, **acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor**.

## What is back emf equation of dc motor?

As the armature rotates, a voltage is generated in its coils. In the case of a generator, the emf of rotation is called the Generated emf or Armature emf and is denoted as Er = Eg. In the case of a motor, the emf of rotation is known as Back emf or Counter emf and represented as **Er = Eb**.

## What will happen if the back emf of dc motor vanishes suddenly?

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.

## What is back EMF formula?

The back emf is calculated based on the difference between the supplied voltage and the loss from the current through the resistance. The power from each device is calculated from one of the power formulas based on the given information. The back emf is **ϵi=ϵS−I(Rf+REa)=120V−(10A)**(2.0Ω)=100V.

## What do you mean by back EMF?

Counter-electromotive force (counter EMF, CEMF), also known as **back electromotive** force (back EMF), is the electromotive force (voltage) that opposes the change in current which induced it. CEMF is the EMF caused by magnetic induction (see Faraday’s law of induction, electromagnetic induction, Lenz’s law).