- #1

jisbon

- 476

- 30

- Homework Statement:
- Find the desired currents and voltages for the circuit below.

- Relevant Equations:
- -

These are my attempts at doing this question, and I was wondering if I am correct so far.

At t= 0-, i(L) will be 0A, since the capacitor acts as a open circuit.

However, I'm not sure why V(c) at t=0- will be -20V as given by the answers. Won't it be 0V?

Moving on, since current in inductor and voltage in capacitor does not change immediately, the values for t=0+ will be the same as t=0-. (Again, I'm not sure why it is -20V for the capacitor, could someone explain to me?)

I'm not sure how to proceed, but if it was me, I will probably transform the circuit? to:

Taking KVL on the left loop,

-80+20i1+ Vc+20=0 --(1)

Taking KVL on right loop,

-20-Vc+40iL+1/L (integerate voltage) -- (2)

I also know Vc = 1/C (integerate i1-iL)

Now the thing is am I making this more complicated than I should? or is this correct so far?

Thanks