# Explain the term self-induction of a coil

**Self – Induction** –

It is the property of an electric circuit or coil by virtue of which it opposes any change of flux or current in it by inducing a current in itself is called self- induction. In another words we can say “**self-induction is the inertia of electricity “.** Due to self -induction an electric circuit resist any change of current through it .

As we know magnetic flux linked with a coil is directly proportional to the current flowing through the circuit

i.e. ɸ α I ( ɸ= flux linked with the coil, and I is the current in the circuit )

ɸ = LI ( L is the constant called coefficient of self- induction or self-inductance or only inductance . )

If current I = 1 ampere, then flux ɸ= L . so we can define self-induction is the flux linked with the coil when unit current passes through the coil.

as we know,

emf e= – dɸ/dt

e= -d (LI)/ dt

e= -L ( dI/dt)

L= – e/(dI/dt)

So we can define self-inductance of a circuit is numerically equal to the induced emf setup in it when the rate of change of current through it is unity.

Unit of self-inductance is Henry (H) . We can define self-inductance of a coil is one Henry if 1 volt emf induced in the coil when rate of change of current through the coil is unity.

To find the expression for self-inductance of long solenoid click here