Homework Help: Energy Stored on a Capacitor

1. May 5, 2008

Strawberry

1. The problem statement, all variables and given/known data
Q18. A 20 F capacitor is charged to 200 V. Its stored energy is:
C. 0.4 J

2. Relevant equations
q = CV
u = .5CV^2

3. The attempt at a solution
I tried plugging in the numbers and got 1.6E6, which isn't even close to the answer. I really don't know where to go with this one. I even went and found an energy calculator online and it came up with the same answer I got. Is stored energy not the potential energy of the capacitor?

2. May 5, 2008

alphysicist

Hi Strawberry,

Are you sure the capacitance wasn't $20 \mbox{ }\mu F$? Most capacitors that I've dealt with in problems are in that range, and that would also give the answer you are given.

3. May 5, 2008

Strawberry

I guess the symbol just didn't show up in the .pdf. Thanks again alphysicist, you've cleared up a ton of things for me in the past few weeks.

4. May 6, 2008

alphysicist

Sure, I'm glad I could help!