# Energy Stored in a Charged Capacitor

1. Dec 8, 2011

### shadyy

1. The problem statement, all variables and given/known data

A 12.0-V battery is connected to a capacitor, resulting in 54.0 μC of charge stored on the capacitor. How much energy is stored in the capacitor?

2. Relevant equations

1/2CV^2

3. The attempt at a solution

At first this problem looks to be easy for me but somehow I get a complete different answer than the back of the book.

I plugged in all the variables and solved and got 3.88 x 10^-4 J

1/2(5.4x10^-6)(12)^2

The answer I get in the back of the book is 3.24 x 10^-4 J

Can someone please explain to me what I am doing wrong?

Last edited: Dec 8, 2011
2. Dec 8, 2011

### MrB8rPhysics

Try finding Q first using C=Q/V, then try 1/2QV. This will either confirm that you are right and the book is wong, or that the book is right and that you are wrong.

3. Dec 8, 2011

### shadyy

Thanks for the quick reply. I tried that and I got a completely different answer. I don't think the book is wrong. I think I'm doing something wrong. I'll try to figure it out I guess.

4. Dec 8, 2011

### technician

Energy stored = 0.5QV
You know Q (charge) and you know V

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook