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## Homework Statement

A 2.00 [tex]\mu[/tex]F capacitor is initially connected to a 12 Volt battery. In a

*separate circuit*, a 4.00 [tex]\mu[/tex]F capacitor is connected to a 30 Volt battery. The capacitors are then disconnected from their respective batteries and connected to

*each other*(positive sides are connected together, and negative sides are connected together). What is the final charge on the 2[tex]\mu[/tex]F capacitor

## Homework Equations

Qtot = Q1 + Q2

.5(C1 V1

^{2}) + .5(C2 V2

^{2}) = .5(C1+C2)V

^{2}

## The Attempt at a Solution

I'm not sure if you use conservation of charge or conservation of energy here. If I use conservation of charge, I get a common V of 24V and charge of 48[tex]\mu[/tex]C on the 2[tex]\mu[/tex]F capacitor.

If I use conservation of energy I get a common V of 25.5 V and a charge of 51[tex]\mu[/tex]C on the 2[tex]\mu[/tex]F capacitor.

The question has some words italicized which means they are probably key words, but I don't really get it. As always, any help is greatly appreciated!