complex RC circuit

Discussion in 'Homework Help' started by google.com, Mar 27, 2005.

Mar 27, 2005
4
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Hi. I've been given a "complex" RC circuit that's been giving me trouble for days. Source is a square wave (-10,10V) but Unit Step is fine for now. As shown in the attachment, the circuit has just a single capacitor so I can reduce the circuit down to a Thevenin Equivalent to get the time constant, total current etc. But I'm looking for the current i(t) through the top resistor, R5, not through the capacitor. This is where I run into trouble..

Since I've found the total current, is setting up a current divider at t=0 and t="infinity" the right approach here? I've done this and my Final values agree but my Initial values (t=0) do not -- I believe this is because at t=0 I treat the capacitor as just a closed circuit ... but this isn't right is it? The current from the cap. is going to flow opposite the current elsewhere.... which to me makes things very complicated.

2. Brandon Senior Member

Dec 14, 2004
306
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Remember, in steady state a cap is an OPEN circuit and a inductor is a SHORT circuit.

This may be the cause of your problem.

Mar 27, 2005
4
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Thanks for the quick response. For the steady state, I do treat it like an open circuit but for the initial (t=0), can I treat it closed?