Question

A constant current exists in a inductor-coil connected to a battery. The coil is short-circuited and the battery is removed. Show that the charge flown through the coil after the short-circuiting is the same as that which flows in one time constant before the short-circuiting.

Answer 1

In this case there is no resistor in the circuit
So, the energy stored due to the inductor before and after removal of battery remains same
$V_1=V_2=\frac{1}{2}L{i}^2$
So, the current will also remain same
Thus charge flowing through the conductor is the same