Electromagnatic Induction
Overview
This Resourse explains the phenomenon of 'Electromagnetin Induction' in a simple manner which is useful for the high school level students.
Introduction
Electromagnetic Induction (EMI) is the phenomenon in which emf is induced in a coil (or conductor) due to change in magnetic flux linked with the coil. This phenomenon of Electromagnetic Induction was discovered by Michael faraday in 1831. To understand this phenomenon, we must know about magnetic flux.
Magnetic Flux (Φ)
Total number of magnetic lines of force passing normally through the given area is called as magnetic flux over that area.
In fig.1 , Circular coin having area 'A' is placed in the magnetic field of induction 'B' and 'n' is the area normal vector which shows the direction which is normal to the given area. As magnetic field component Bcosθ is passing normally thorugh the unit area of the coil, magnetic flux for the coil having area 'A' will be
Φm = BAcosθ
If the cirular coil has 'N' number of turns
then Φm = NBAcosθ
Faraday's Laws of Electromagnetic Induction
In this experiment, Faraday used one coil with its ends connected to the sensitve ammeter and one magnet pointing towards the coil.
Faraday observed that,
- when magnet is stationary with respect to the coil, no deflection is observed in an ammeter.
- when magnet is moved towards or away from the coil, ammeter gives deflection.
- If motion of the magnet is faster, deflection oberved in an ammmeter is greater.
From these observations, Faraday conclude that, motion of magnet towards or away from the coil causes change in magnetic flux linked withe coil and due to change in magnetic flux linked with the coil emf is induced and current is produced in the coil.
Faraday's 1st Law of EMI
Whenever there is change in magnetic flux linked with the coil, EMF is induced in the coil.
Faraday's 2nd Law of EMI
The magnitude of induced emf |e| in a coil is directly proportional to the rate of change of magnetic flux ( dΦ /dt ) linked with the coil.