An emf of 0.5 V is developed in the secondary coil, when current in primary coil changes from 5.0 A to 2.0 A in 300 milliseconds. The mutual inductance of two coils would be:

0.05 H

The correct answer is Option (4) → 0.05 H

The mutual inductance (M) can be calculated using -

$emf=M\frac{ΔI}{Δt}$

$emf=0.5V$

$ΔI$ = Change in current = $5 - 2 = 3A$

$Δt = 300 ms = 0.35 s$

$∴M=\frac{0.5×0.3}{3}=\frac{0.15}{3}=0.05H$