The question that I'm trying to solve is as follows:
In the circuit shown below, the switch has been closed for a long time. a) What is v(0) or the voltage across the capacitor immediately after the switch is opened? b) What is i(0) and i1(0)?
First, I calculated for the voltage before t = 0 using voltage division. I arrived at v(0-) = 4V. Since the capacitor voltage cannot change instantaneously, I assumed that 4V is the voltage at t=0.
Here's the tricky part. I'm asked to find the current at t = 0. By looking at the diagram, I am certain that the 1-ohm resistor is short-circuited, so I simply dismissed that and used Ohm's Law to find i1(0-) using v = 20 V and R = 4 ohms. In the property of short circuit, the i is equal to 0.
Are my solutions for i1 and i legal to begin with? I'm only confident with 4V as the voltage at t = 0.