I am trying to solve this question:
However, I am having difficulties solving as I only have come across circuits which are initially closed then opened, not vice versa as is the case here. Specifically, I am trying to construct the simplified circuit for
t<0. Usually, for the latter case, the inductor is a short circuit for the 20 Ohm resistor if t<0. However, I am unsure how it acts as this circuit starts open and then becomes closed.
So far, all I have been able to do is to a source transformation, making the current source a 150 V voltage source and combining the 10 and 5 Ohm resistors.
Any help would be appreciated, thanks!