**i) Self-inductance:** It is the property by virtue of which a coil opposes change in current flowing through it by inducing an emf in it such that its effect is to circulate current (induced current) that produces a magnetic field which opposes the change in the field.

OR

**Equation for self-inductance:**

L dΦ/dt or L = dΦ/I or L = N^{2}/S

where, L is the coefficient of self-inductance, N is the no. of turns of coil, d∅ is the change in the flux, di is the change in current, S is the reluctance of magnetic path.

**ii) Coefficient of self induction:** Coefficient of self- induction of a coil is defined as the ratio of the electromotive force produced in a coil by self-induction to the rate of change of current producing it.

L NdΦ/dt / di/dt N = di/dt N = Φ/I

It is expressed in henry.