W=qV vs 1/2(CV^2)

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herewego

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Could someone explain when to use one or the other, in reference to capacitors?

In the PR physics practice passages, I've seen questions worded similar to "How much work must be done to move X" or "How much work must be done against the electric field," with both of those equations used, so I'm a little confused about the nuance of when to use one or the other.

Any help would be appreciated.

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Could someone explain when to use one or the other, in reference to capacitors?

In the PR physics practice passages, I've seen questions worded similar to "How much work must be done to move X" or "How much work must be done against the electric field," with both of those equations used, so I'm a little confused about the nuance of when to use one or the other.

Any help would be appreciated.

I had the same issue using TPR. I thought that the cv^2/2 equation was only for storing energy in capacitators but it seems you can apply it to these problems. I am not sure what I'm about to say is correct but after comparing questions and answers i came to the conclusion that for these particular problems, you could have used either equation - it just depends on what variables you are given in the question. Now i could be wrong but thats the only thing i could figure out about this situation - there were like 4 questions spread across 4 different passages if you are using the same TPR science workbook i did.
 
Yep, we're on the same page, literally and metaphorically.

But sometimes they aren't interchangeable either. just compare W=QV to 1/2(QV). You're off by a factor of 1/2, but using the same variables.

So I dunno..

Can anyone else chime in?
 
Yep, we're on the same page, literally and metaphorically.

But sometimes they aren't interchangeable either. just compare W=QV to 1/2(QV). You're off by a factor of 1/2, but using the same variables.

So I dunno..

Can anyone else chime in?

Not sure the Q's are the same in this case. One is the charge of the capacitator (Q), the other is the charge on the electron/proton (usually these particles are the one's being talked about). This is the W=qV equation.
 
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I think W = qV is more for moving just one or a set number of charges across a voltage difference V (ie a capacitor) while W = 1/2QV is the work required to fully charge, or move ALL of the charges, across a capacitor to fully charge it
 
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