Inductance of a coil is numerically equal to the emf induce din the coil when the current in the coil changes at the rate of 1 As−1. If I is the current flowing in the circuit, then flux linked with the circuit is observed to be proportional to I, i.e., ϕ∝I or ϕ=LI.....(i) Where L is called the self – inductance or coefficient of self-inductance or simply inductance of the coil. Net flux through solenoid, ϕ=500×4×10−3=2Wb or 2=L×2 [after putting values in Eq.(i)] or L=1H