Mutual inductance of a pair of coils, μ = 1.5 H

Initial current, I₁= 0 A Final current I₂ = 20 A

Change in current, dl = I₂ — I₁= 20 — 0 = 20 A

Time taken for the change, t = 0.5 s

Induced emf e = dφ/dt ——————Eq-1

Where, dφ is the change in the flux linkage with the coil.

Emf is related with mutual inductance as:

e = μ dI /dt —————————-Eq-2

Equating equations (1) and (2), we get

dφ/dt = μ dI /dt

dφ = 1.5x(20)

= 30 Wb

Hence, the change in the flux linkage is 30 Wb.