Question

What causes back-EMF in an electric motor?

   What causes back-EMF in an electric motor?

Physics Principle and Problems

Physics Principle and Problems

Paul W. Zitzewitz,… 1st Edition

Chapter 25, Problem 38

Instant Answer

Solved by Expert Mayukh Banik

05/29/2020

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This can be represented as: \[ \text{Motor} = \text{Coils} + \text{Magnetic Field} \] Show more…

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What causes back-EMF in an electric motor?

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Key Concepts

Electromagnetic Induction

This principle states that a voltage is generated across a conductor when it is exposed to a changing magnetic field. In the context of electric motors, as the motor's coils rotate within a magnetic field, the magnetic flux through the coils changes continuously, inducing a voltage in them.

Faraday’s Law of Induction

Faraday’s Law quantifies electromagnetic induction by stating that the induced electromotive force in a circuit is proportional to the rate of change of magnetic flux through the circuit. This law explains how the movement of a motor's components within a magnetic field produces an induced voltage.

Lenz’s Law

Lenz’s Law provides the direction of the induced electromotive force, stating that it will oppose the change in magnetic flux that produced it. In electric motors, this opposition manifests as a back-EMF that counters the applied voltage, thereby influencing the net voltage and current in the motor.

Motor as a Generator Concept

When a motor operates, its rotating parts convert mechanical energy to electrical energy through electromagnetic induction, effectively acting as a generator. This generated voltage, known as back-EMF, opposes the applied input voltage. It helps regulate the motor’s performance and protects it from drawing excess current.

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