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\begin{figure}\centerline{
\psfig{file=problems/prob_5_1.eps,height=2.5in}
}\end{figure}

A pair of capacitors $C_1$ and $C_2$ is connected as shown, with a resistance $R$ in between them. Initially, the first capacitor carries a total charge $Q_{1i}$ and the second one is uncharged, $Q_{2i} = 0$. At $t = 0$ the switch is closed. Find:

a) The equilibrium ($t = \infty$) charges on the two capacitors, $Q_{1f}$ and $Q_{2f}$.

b) Using Kirchoff's laws for this arrangement, find the time constant for the equilibration process. Note that you do NOT have to solve the DE, just formulate it with $dt$ and some arrangement of $R$, $C_1$, and $C_2$ on the other side.

c) For extra credit, either solve the DE (it is integrable, although a bit messy) or GUESS what its solution is, based on your answers to a) and b). To do the latter, try visualizing what $Q_1(t)$ and $Q_2(t)$ will formally look like - it is just a matter of setting the various constants so that the asymptotic (final) and initial conditions are correctly represented and the approach to those conditions has the right time dependence.


next up previous contents
Next: . Up: Resistors and RC Circuits Previous: Resistors and RC Circuits   Contents
Robert G. Brown 2003-02-09