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Work to Move parallel capacitor Plates 
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#1
Mar2713, 04:10 AM

P: 43

Hi, in my book there are two capacitor plates distance x apart (they are kept connected to a constant voltage source). These plates are moved apart to distance 3x. In order to find the work done to move the capacitors apart (using W=F dl=QE dl), my book takes the charge Q of one plate and electric field felt on that one plate and integrates it from x to 3x. Why can't we take the take the charge and electric field felt on both plates and integrate half the distance of x to 3x?



#2
Mar2713, 04:51 AM

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#3
Mar2713, 02:24 PM

P: 43




#4
Mar2713, 02:55 PM

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P: 41,440

Work to Move parallel capacitor Plates
Compare that to just moving one plate (like in your book). In that case y would be the total distance, so L = y. And you'd integrate from y = x to y = 3x. (And not multiply by 2.) Each method should give the same answer for the work done. 


#5
Mar2713, 03:14 PM

P: 43




#6
Mar2713, 03:36 PM

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P: 41,440




#7
Mar2713, 04:07 PM

P: 43




#8
Mar2713, 04:19 PM

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#9
Mar2713, 04:32 PM

P: 43




#10
Mar2713, 05:39 PM

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But since the two plates experience the same force and movement, why not take advantage of symmetry? 


#11
Mar2713, 06:03 PM

P: 43

Thanks!



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