Question

A carspark coil developes an induced e.m.f. of 40000 V in the secondary when when current in primary changes form 4 A to zero in `10 mu s`. What is the mutual inductance of the coil ?

Answer 1

Here, `e = 40000 V, dI = 0 - 4 = - 4 A`.
`dt = 10 mu s = 10^(-5) s, M = ?`
As `|e| = M (dI)/(dt)`,
`M = |e| (dt)/(dt) = (40000 xx 10^(-5))/(4) = 0.1 H`