A 12 V battery connected to a coil of resistance $6 \Omega$ through a switch. drives a constant curr

Question

A 12 V battery connected to a coil of resistance $6 \Omega$ through a switch. drives a constant current in the circuit. The switch is opened in 1 ms . Theemf induced across the coil is 20 V . The inductance of the coil is

Professor PC Thomas Classes · Answer

Current $I = V/R = 12/6 = 2$ A. Induced emf $E = L\frac{di}{dt} \Rightarrow 20 = L \frac{2}{10^{-3}} \Rightarrow L = 10$ mH.