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## Homework Statement

Capacitors of 19.1 uF and 2.1 uF are charged as a parallel combination across a 229 V battery. The capacitors are disconnected from the battery and from each other. They are then connected positive plate to negative plate and negative plate to positive plate.

Find the resulting charge on the ﬁrst capacitor.

## Homework Equations

Q = CV

## The Attempt at a Solution

Since they are connected in parallel, I found the charge for each individual capacitor.

Q1 = C1V

Q2 = C2V

Then I know when reconnected, the net charge has to equal the new charge. So:

q1+q2 = Q1-Q2

Then the voltage across them has to be the same. So:

V' = q1/c1 = q2/c2

Then I solved them sim. and got:

q1 + (c2/c1)q1 = Q1 - Q2

But when I plug in my numbers, I get the wrong answer. What am I doing wrong?

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