# Homework Help: Capacitance Circuit - Voltage and Charge

1. Sep 22, 2009

### PerfPhys

1. The Question
a. What is the equivalent capacitance of the combination shown in the figure ?
b. If a 100V battery is connected across the combination, what is the charge on each capacitor?
c. What is the voltage across each?

2. Equations

3. Solution attempt
For part a, I added C2 and C3 to get .03, then added the two in series (1/.02)+(1/.03) and took the inverse to get a combination capacitance of .012 microF

I am stuck on parts b and c, though. For B, we know Q=V/C and for C2 it would be Q=(100V)(0.01microfarads) which gives a charge of 1 microcoulomb.

for C3 it would be Q=(100V)(.02microfarads)=2 microcoulombs.
And for C1 it would be Q=(100V)(.02microF)= 2 microcoulombs.

However this answer is not working.

For part C, I tried plugging the charge and C in to the same equation to get the V back out, but again this has not worked. I'm not sure if my units are off, or if I am missing something conceptually.[/b]

Any help would be appreciated!

2. Sep 22, 2009

### PerfPhys

Nevermind, I just figured it out - I was trying to use the individual capacitance of C2 and C3 when I should have been using the combined since they are in parallel. :)