# RLC circuit, initial and final conditions.

Discussion in 'Homework Help' started by wiz0r, Oct 18, 2008.

1. ### wiz0r Thread Starter Active Member

May 2, 2008
64
0
Hello!

I got the following problem to solve(it is "circuito" in the attachment).

So, I have to find the initial and final conditions of the RLC circuit.

Ok, I have to evaluate at t = 0, and t = infinite, right?

So, at t = 0 the first switch is open, the second one is closed, and the capacitor will act as an open circuit, and the inductor as a short circuit, right?

Making some calcs I got that;

i(0) = 8/3 Amps, is that correct?

Now, at t = infinite, the first switch is closed, the second one is open, and the capacitor will act as an open circuit, and the inductor as a short circuit, right?

So, with some calcs I got;

i(infinite) = 5 Amps, correct?

Anyway, I wanted to verify that what I did was correct. If I'm not correct, please post it and I will post my calculations, and then we can see what I did wrong.

Thanks.

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2. ### Ratch New Member

Mar 20, 2007
1,068
3
wiz0r,

Your analysis and results are both correct.

Ratch

3. ### wiz0r Thread Starter Active Member

May 2, 2008
64
0
Great, thank you, Ratch.

4. ### hitmen Active Member

Sep 21, 2008
159
0
I have a question. How are you going to find Rth?? How are you going to find the differential equation?

5. ### luna Member

Oct 19, 2008
12
0
the Rth you can find it like this:
RL=Rth
Rth=R2*R1/R1+R2
but this is for Thevenin equvalent Circuits