Problem 6: Current in a circuit falls from 5.0 A to 0 A in 0.1 s. If an average emf of 200 V induced, give an estimate of the self-inductance of the circuit?

Solution

Given data                         Initial current in the circuit = 5.0 A

                                             Final current in the circuit = 0 A

                                             Average emf = ε                 = 200 V

                                             Time                                        = 0.1 s

Asked                                  Self-inductance, L

Formula

Now, change in the current in the circuit = 5 A

(Note that the change in the current is negative but it shows only the current is decreasing and has nothing to do with the inductance of the circuit. Also note, decrease in current shows the polarity of the emf).

From the given data,                      (ΔI/Δt) = 5/0.1 = 50 As^-1  (We ignore the negative sign).

Apply the formula,