# Electromagnetic Induction - Definition, Applications and Eddy Currents

During electromagnetic induction, the electromagnetic field of a conductor interacts with a magnetic field to produce an electromotive force (EMF). Michael Faraday discovered it in 1831 and it forms the basis for almost all electrical devices, including power plants, electric motors, transformers, circuitry, and many other things.

Induction occurs in coiled wires when there is a change in magnetic field, which results in voltage (EMF) being produced. In addition to changing the strength of the magnetic field, Faraday found ways to move a magnet through a coil of wire, and move the coil through a magnetic field as well.

## What is Electromagnetic Induction?

The law of electromagnetic induction was formulated mathematically by James Clerk Maxwell in 1831 based on Faraday's discovery.

A current is produced when magnetic field changes lead to voltage production (electromotive force). In alternating current (AC), this occurs as the conductors are placed in a moving magnetic field (due to a change in the nature of AC). In stationary power (direct current), it occurs when conductors are constantly moving.

Faraday performed an experiment where the voltage across a circuit was measured by attaching a conducting wire to a measuring device. The voltage detector measured the voltage in the circuit as the bar magnet was pushed through the coiling. There was a change in voltage measured which suggested that a current is flowing when the bar magnet was moved through the coil center, bringing about a change in magnetic flux.

A number of factors influence this voltage production, which Faraday discovered in his experiment. The factors are as follows:

1. Coil count. There is a direct relationship between the induced voltage and the number of turns/coils in the wire. When there are more turns, the voltage will be greater.
2. Constant Change in Magnetic Fields. The induced voltage changes with changing magnetic fields. It is possible to move the magnetic field around the conductor or move the conductor within the magnetic field.

The amount of voltage induced in a coil is proportional to the number of turns of the coil and the rate at which the magnetic field is changing. Faraday established this law through his experiments.

## Electromagnetic induction and its applications

The applications of the Electromagnetic Induction are given below:

• Electromagnetic induction is the principle behind AC generators.
• Electromagnetic induction is responsible for the working of electrical transformers.
• Magnetic flow meters use electromagnetic induction to operate.

The formula for electromagnetic induction

According to the following relation on electromagnetic induction, we can calculate the induced voltage:

e= N dΦ/dt

Where,

• e represents the induced EMF
• N represents the number of turns present in the coil
• Φ represents the magnetic flux
• t represents the time

The significance of this discovery lies in the fact that it uses magnetic fields instead of batteries to generate electrical energy in a circuit. The principle of electromagnetic induction is used in everyday appliances like motors, generators, and transformers.

## Eddy currents

According to Lenz's law of electromagnetic induction, the current creates a magnetic field that opposes the current flow. A loss of energy is caused by eddy currents due to their tendency to oppose. Eddy currents lead to waste generation by converting the useful forms of energy into useless heat energy. However, there are some applications in which it is desirable to lose useful energy. Examples include:

• It can be found in the brakes of some trains. Eddy currents are generated when the brakes are applied to metal wheels. Eddy currents and the applied field interact magnetically to slow the wheels down. The higher the speed of the wheels, the greater is the effect. This result in smooth braking system as when the train starts to slow down, the force gradually decreases.
• There are few galvanometers made from nonmagnetic metallic materials with a fixed core. Coil oscillations are opposed by eddy currents generated within the core, causing the coil to rest.
• Induction furnaces can be used to melt metals to prepare alloys. It induces metals to generate eddy currents that create high temperatures that melt the metals.
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