Question

A toroidal coil has an inductance of 47 mH. Find the maximum self-induced emf in the coil when the current in it is reversed from 15 A to -15 A in 0.01 s.

Answer 1

Data : L = 4.7 × 10^-2 H, 

I_i = 15A, I_i = -15 A, 

∆f = 0.01 s

The rate of change of current,

 \(\cfrac{dI}{dt}\) = \(\cfrac {I_f−I_i}{Δt}\) = \(\cfrac{(−15)-15}{0.01}\) = – 3000 A/s

∴ The maximum self-induced emf,

e = – L \(\cfrac{dI}{dt}\) (4.7 × 10^-2) (- 3000) = 141 V