A current of 10 A in primary of a circuit is reduced to zero at a uniform rate in $10^{-3}$s. If coeff. of mutual inductance is 3 H, the induced emf in the secondary would be:

$3 × 10^4 V$

The correct answer is Option (2) → $3 × 10^4 V$

According to faraday's law,

$ε=-M\frac{dI}{dt}=-M\frac{ΔI}{Δt}$

$=-(3H)\frac{10A-0}{10^{-3}}=-3 × 10^4 V$