Energy Stored in a Charged Capacitor

  • Thread starter shadyy
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  • #1
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Homework Statement



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?


Homework Equations



1/2CV^2

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:

Answers and Replies

  • #2

Homework Statement



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?


Homework Equations



1/2CV^2

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^-6 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?

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
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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
1,506
18
Energy stored = 0.5QV
You know Q (charge) and you know V
 

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