Electromagnetic Induction

DefinitionDefinition The process of generating an electromotive force The process of generating an electromotive force

by moving a conductor through a magnetic field by moving a conductor through a magnetic field is known as electromagnetic magnetic induction.is known as electromagnetic magnetic induction.

In simpler words we can say that production of In simpler words we can say that production of electricity from magnetism is called electricity from magnetism is called electromagnetic induction.electromagnetic induction.

DiscovererDiscoverer!!!!!! Michael Faraday is Michael Faraday is

generally credited with the generally credited with the discovery of induction in discovery of induction in 1831 though it may have 1831 though it may have been anticipated by the been anticipated by the work of Francesco work of Francesco Zantedeschi in 1829. Zantedeschi in 1829. Around 1830 to 1832 Around 1830 to 1832 Joseph Henry made a Joseph Henry made a similar discovery, but did similar discovery, but did not publish his findings not publish his findings until later.until later.

Verifying Faraday’s Verifying Faraday’s ExperimentExperiment

Wind an insulated Wind an insulated wire over a hollow wire over a hollow cylinder to make a cylinder to make a coil.coil.

Connect a Connect a galvanometer to galvanometer to the coil.the coil.

Cont….Cont….

Move a powerful Move a powerful magnet in and out magnet in and out of the coil.of the coil.

ObservationObservation

When the magnet is When the magnet is moved in, the moved in, the galvinometer needle galvinometer needle deflects towards the deflects towards the left.left.

When the magnet is When the magnet is moved out, the moved out, the galvinometer needle galvinometer needle deflects towards the deflects towards the right.right.

Cont…Cont…

When the magnet When the magnet is stationary, the is stationary, the galvanometer galvanometer needle returns to needle returns to zero.zero.

ResultResult

The deflection of the The deflection of the needle, when the magnet needle, when the magnet is moved in or out, is moved in or out, indicates that a current indicates that a current has been induced in the has been induced in the coil.coil.

An emf is induced in the An emf is induced in the coil due to the movement coil due to the movement of the magnet.of the magnet.

A moving magnetic field A moving magnetic field is necessary for is necessary for electromagnetic electromagnetic induction.induction.

Inducing emfInducing emf

Inducing emf using two coilsInducing emf using two coils

In this case a coil In this case a coil is connected to a is connected to a battery and a battery and a switch.switch.

Then a second Then a second coil is taken which coil is taken which is connected to is connected to the galvanometer.the galvanometer.

Cont…Cont…

When the current is When the current is allowed to flow in the allowed to flow in the primary coil, a primary coil, a magnetic field is magnetic field is generated around it.generated around it.

The magnetic field The magnetic field associated with the associated with the second coil also second coil also increases equally.increases equally.

This induces emf in This induces emf in the secondary coil.the secondary coil.

Direction of motion of the Direction of motion of the MagnetMagnet

The direction of the The direction of the motion of the motion of the magnet determines magnet determines the direction of the the direction of the induced current.induced current.

The direction of the The direction of the induced emf induced emf changes according changes according to the motion.to the motion.

Orientation of the magnetOrientation of the magnet

The direction of the The direction of the induced emf induced emf changes if the changes if the magnet is inserted magnet is inserted with the reverse with the reverse pole.pole.

Speed of the magnetSpeed of the magnet

The speed of the The speed of the magnet determines magnet determines the strength of the the strength of the induced emf.induced emf.

Higher the speed, Higher the speed, higher the emf higher the emf induced.induced.

Strength of the magnetStrength of the magnet The strength of the The strength of the

magnet also magnet also determines the determines the amount of emf amount of emf induced.induced.

The amount of emf The amount of emf induced is directly induced is directly proportional to the proportional to the strength of the strength of the magnet.magnet.

Number of turns in the coilNumber of turns in the coil

The number of The number of turns in the coil turns in the coil also determines also determines the induced emf.the induced emf.

Higher the number Higher the number of turns, higher the of turns, higher the emf induced.emf induced.

Faraday’s LawFaraday’s Law

The magnitude of The magnitude of induced emf, E, in induced emf, E, in any closed circuit any closed circuit is directly is directly proportional to the proportional to the rate of change of rate of change of magnetic flux, magnetic flux, through the circuit.through the circuit.

Fleming’s Right Hand RuleFleming’s Right Hand Rule(The Generator rule)(The Generator rule)

Stretch the thumb, the Stretch the thumb, the forefinger and the forefinger and the middlefinger of your middlefinger of your hands in mutuallly hands in mutuallly perpendicular directions.perpendicular directions.

Then the thumb Then the thumb represents the motion of represents the motion of charge and the charge and the forefinger and middle forefinger and middle finger represent the finger represent the magnetic field and the magnetic field and the electric current electric current respectively.respectively.

ExampleExample

Now consider a Now consider a conductor AB conductor AB connected to a connected to a galvanometer and galvanometer and placed in a placed in a magnetic field.magnetic field.

When we move When we move the conductor the conductor downwards in downwards in the magnetic the magnetic field, the field, the galvanometer galvanometer needle deflects needle deflects towards left.towards left.

This indicates This indicates the direction of the direction of the current in the current in the conductor the conductor from B to A.from B to A.

Electric GeneratorsElectric Generators

Generators work on Generators work on the principle of the principle of electromagnetic electromagnetic induction.induction.

They are used to They are used to generate electricity.generate electricity.

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