# What is meant by back emf in dc motor?

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## What is meant 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).

## What is back emf in DC motor Quora?

The Back EMF is the Inductive collapsing current induced back into the coils of the DC motor, caused by the collapsing voltage/ reversing current and eddy current repulsion.

## What is the role of back EMF?

The significance of Back EMF

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 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.

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## What is effect of back EMF in motor?

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 Quora?

Back emf is actually the emf produced at the armature winding, due to the rotation of the rotor. back emf is responsible for the rotor rotation. it is also called as counter emf as it is opposite polarity to the supply voltage. basic importance is the motor can be operated as a generator.

## 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. Circuit diagram and example taken from New South Wales, Department of Education and Training, 2007.

## What is back emf voltage?

Back electromotive force (back EMF, BEMF) is a voltage that appears in the opposite direction to current flow as a result of the motor’s coils moving relative to a magnetic field. It is this voltage that serves as the principle of operation for a generator.

## What is difference between emf and back EMF?

EMF (or Electro Motive Force) is the voltage applied to the motor from an external power supply. Back EMF is the voltage produced within the motor windings which is opposite polarity but smaller than the applied voltage. Think of a motor as also being a generator.

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## What is back EMF in relay?

If the coil is de-energised, the collapsing magnetic field in the coil as the armature moves away from the coil, generates a reverse voltage spike across the coil terminals – this is called “Back EMF (Electromotive Force).