In $($Figure $1),$ suppose that $E=56\mathrm{.}0V,R=250\mathrm{.}0$ and $L=0\mathrm{.}170H.$ With switch $S_2$ open, switch $S_1$ is left closed until a constant current is established. Then $S_2$ is closed and $S_1$ opened, taking the battery out of the circuit.