What is self inductance and coefficient of self inductance ?

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 When a current passing through a coil changes, the magnetic flux (`\Phi`) linked with the coil also changes.

The change in magnetic flux linked with the coil causes an electromotive force (e.m.f) to induce in the coil itself. Such a phenomenon of induction of e.m.f in  a coil by passing the changing current or alternating current through it is called self induction.



Fig.1 Faraday's law of electromagnetic induction


The magnitude of induced e.m.f is given by Faraday's laws of electromagnetic induction. By this law, the self induced e.m.f (`e_s`) is directly proportional to the time rate of change of magnetic flux linked to the coil. That is,

`e_s \prop \frac{d \Phi}{dt} ------(1)`

But time rate of change of magnetic flux is directly proportional to time rate change of induced current(I).  That is,

`\frac{d \Phi}{dt} \prop \frac{dI}{dt} ------(2)`

Combining (1) and (2),

`e_s \prop \frac{dI}{dt} `

` \therefore   e_s = -L \times \frac{dI}{dt} ------(3)`

Where L is constant inductance of coil, called  coefficient of self inductance.

Also from(3),

` L = - \frac{e_s}{frac{dI}{dt}} ----(4)`

So, L can also be defined as the induced e.m.f per unit rate of change of current induced in itself.


πŸ‘‰ Click on link for NEB grade 12  physics numerical problem-solutions:- LINK

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