When current changes from 13 A to 7 A in 0.5 second through a coil, the e.m.f. induced is 3 x 10-4 V. What is the coefficient of self induction?

25 x 10-3 H     25 x 10-4 H   25 x 10-5 H     25 x 10-6 H

25 x 10-6 H

$\xi = L\frac{\Delta L}{\Delta t} $ $ L = \xi \frac{\Delta t}{\Delta L} = 3\times 10^{-4} \frac{0.5}{6} = 25\times 10^{-6}H$