If I have this circuit in which the switch opens at t = 0 (after being closed for an infinite time, making the circuit steady state), for which I'm trying to find the voltage across R2 as a function of time, I need to determine the current through the inductor as a function of time first. To do this, I need to find the initial current through the inductor. (ignore element values)
I can replace the inductor with a short circuit and use circuit simplifications to reduce the circuit to the following. This is before the switch is opened at t = 0, and use the current through this circuit as the initial current through the inductor.
After t = 0, my gut tells me I can simplify the circuit into two parts, one containing the inductor, and the other without.
What law states I can do this? Is it because opening the switch means there are no current loops between either side of the circuit?
Thanks for your help!