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Homework Help: Energy Stored in a Charged Capacitor

  1. Dec 8, 2011 #1
    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. jcsd
  3. Dec 8, 2011 #2
    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.
     
  4. Dec 8, 2011 #3
    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.
     
  5. Dec 8, 2011 #4
    Energy stored = 0.5QV
    You know Q (charge) and you know V
     
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