- #1
juicec
- 19
- 0
Homework Statement
First off, thanks for taking a look at my problem guys. I have been given this question as extra credit for a calc-physics II class and at the moment am struggling with pulling the pieces together. At first glance I didn't have to much trouble with it but when I go back to it to write it up, it begins to make less and less sense. We didn't really do a whole lot of RC circuit stuff in this summer term which is why I think in part he gave us this question, so I'm really just here to get some confirmation, some help and a little advice where ever possible.
So here it goes:
Find the time constant and the explicit time dependence for all currents. Assume that the capacitor is initially uncharged when switch S is closed. Make plots of the currents clearly indicating any features characteristic of the system.
You can view the diagram/full question here: http://www.scribd.com/doc/59234592/Problem-2
Homework Equations
We've got the charging/discharging formulas for RC circuits.
tao = RC
Series/parallel relationships.
The Attempt at a Solution
The plots are not an issue for me, the jist of it would be that at t=0, the capacitor drains all the current from the circuit, and the current exponentially decreases to infinity. At the same time the charge will have an exponential increase to a plateau.
My real issue stems from being unable to identify with reducing the circuit down into an effective resistance. When trying to calculate the time constants, for example where it goes from Battery -> R1 -> R2 -> battery, it is clear that R2 and C are in parallel, but at the same time R1 is in series to R2C. So I am thinking do we use the 1/jwc (resistance of a capacitor. We haven't actually learned this yet but I've read it online) and reduce the circuit into an effective resistance as you would any other regular R or C circuits. Basically what it comes down to is if someone could help me with one of the loops, I think I could take it from there. I am just unsure what exactly is our resistance and what exactly is our capacitance and how does the effective circuits come into play.
Again I am new to RC circuits in general but have a solid understanding of your basic R and C circuits.
Thanks in advance for any help provided, I'm under a pretty tight deadline and hope to hear from someone soon :)