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Capacitors  energy stored vs work done 
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#1
Jan2511, 12:59 PM

P: 90

this isnt homework, im doing revision for an exam :)
a 180 microfarad capacitor is charged so that is has a PD of 100v across the plates. i calculate the energy stored as 0.5cv˛ = 0.9J the question then asks me to calculate the work done by the battery in charging the capacitor. the mark scheme says that i should use W = QV = CV˛ and should therefore get 1.8J why is the work done in charging the capacitor different to the energy stored on it? i have never heard my teacher mention this fact in lessons, so i seriously have no idea where this has come from.. where does this equation come from? thanks 


#2
Jan2511, 01:06 PM

P: 3,387




#3
Jan2511, 01:08 PM

P: 90




#4
Jan2511, 01:14 PM

P: 3,387

Capacitors  energy stored vs work done
If you work through the calcs you'll see that half the energy is lost when charging. Here is a similar thread answering the question for you: http://www.physicsforums.com/showthread.php?t=292838 


#5
Jan2511, 04:14 PM

P: 90

okay thanks, although im not sure i understand that thread particularly well :/ 


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