SELF INDUCTION
Self induction is that phenomenon in which a change in electric current in a coil produces an induced emf in the coil itself.
MATHEMATICAL REPRESENTATION:
Self induced emf in a coil is directly proportional to the rate of change of electric current in the coil.i.e.
Emf a – DI/Dt

Or emf = -L DI/Dt

Where, L = self inductance of the coil.

SELF INDUCTANCE
Self inductance of a coil is defined as the ratio of self-induced emf to the rate of change of current in the coil.
Self inductance = emf/ DI/Dt
It is denoted by ‘L’ and it depends upon the physical characteristics of the coil.

Unit of self inductance is Henry.





HENRY
For latest information , free computer courses and high impact notes visit : citycollegiate.com
The self inductance of a coil is one henry if a current change of one ampere per second through it produces an emf of one volt in it.


If a changing flux is linked with a coil of a conductor there would be an emf induced in it. The property of the coil of inducing emf due to the changing flux linked with it is known as inductance of the coil. Due to this property all electrical coil can be referred as inductor. In other way, an inductor can be defined as an energy storage device which stores energy in form of magnetic field.

Theory of Inductor

A current through a conductor produces a magnetic field surround it. The strength of this field depends upon the value of current passing through the conductor. The direction of the magnetic field is found using the right hand grip rule, which shown. The flux pattern for this magnetic field would be number of concentric circle perpendicular to the detection of current.
Now if we wound the conductor in form of a coil or solenoid, it can be assumed that there will be concentric circular flux lines for each individual turn of the coil as shown. But it is not possible practically, as if concentric circular flux lines for each individual turn exist, they will intersect each other. However, since lines of flux cannot intersect, the flux lines for individual turn will distort to form complete flux loops around the whole coil as shown. This flux pattern of a current carrying coil is similar to a flux pattern of a bar magnet as shown.
inductor
Now if the current through the coil is changed, the magnetic flux produced by it will also be changed at same rate. As the flux is already surrounds the coil, this changing flux obviously links the coil. Now according to Faraday’s law of electromagnetic induction, if changing flux links with a coil, there would be an induced emf in it. Again as per Lenz’s law this induced emf opposes every cause of producing it. Hence, the induced emf is in opposite of the applied voltage across the coil.

Definition of Self Inductance

Whenever, current flows through a circuit or coil, flux is produced surround it and this flux also links with the coil itself. Self induced emf in a coil is produced due to its own changing flux and changing flux is caused by changing current in the coil. So, it can be concluded that self-induced emf is ultimately due to changing current in the coil itself. And self inductance is the property of a coil or solenoid, which causes a self-induced emf to be produced, when the current through it changes.
Explanation of Self Inductance of a Coil