1. The problem statement: What is the value of capacitance needed in Fig. 1 so that the voltage across the capacitor never exceeds (a) 200 V, (b) 20 V, and (c) 2 V ? This is the Circuit 2. Relevant equations Vc(0-) = 0V Vc(0+) = 150V ic = c v' vc(t) = final + [initial - final] e^(-t/τau) 3. The attempt at a solution since the capacitor is in parallel with the resistor the voltages are equal. which at t=0 will be 150V. up until 100us the capacitor is charging, then when t>100us the capacitor will discharge. so the max voltage across the capacitor will be 150V no matter what the value is. However you can get a smaller capacitance value to decrease this voltage but the voltage will never exceed 150V. I broke the problem into two transient problems: (1) t=0+ and t=100us- (2) t=100us+ and t=infinity- I tried to solve for Vc(t) for each of these problems: for (1) Vc(t) = 20 - 20e^(-t/c) for (2) Vc(t) = 20e^(-t/2c) This did not work out right. So then I tried converting to non ideal current source, but got stuck. 4.PROBLEM - I have never done a transient problem where the switch changes at some value other then 0. -I simulated this circuit on pspice and I get the capacitance for each voltage, BUT I want to know how to do this by hand. Your help is much appreciated!!