2-Resistor, 2-Capacitor Circuit with Switch

Mark Zhu

Problem Statement
In the circuit below, find the charges on the capacitors a) if the switch is open, b) if the switch is closed. Here C1 = 1 microfarads, C2 = 4 microfarads, R1 = 20 ohms and R2 = 40 ohms.
Relevant Equations
V = iR
Q = CV
I already did part a and got the correct answer of 4.8 microC. However, I am unsure how to approach part b, where the switch is closed and apparently the two capacitors end up with different charges. For part b, since there is a path between the two capacitors, I don't know if I am able to combine the two capacitors into an equivalent capacitor. According to the textbook, the solution is that Q1 is 2 microC and Q2 is 16 microC. Any help is appreciated. Related Introductory Physics Homework News on Phys.org

BvU

Homework Helper
Hi,

Well, what do you get for the voltage over C1 if you apply your first relevant equation ?

(after you determined -- qualitatively -- what happens with the current through the switch when it is closed and afterwards )

Mark Zhu

I think I got it, thank you.

BvU

Homework Helper
With the answers given it's a piece of cake "2-Resistor, 2-Capacitor Circuit with Switch"

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