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.
Equation for self-inductance:
L dΦ/dt or L = dΦ/I or L = N2/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.