Find the initial total charge stored

  • Thread starter thst1003
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  • #1
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Initially a 1.52 µF capacitor and a 2.63 µF capacitor are connected in parallel, with 9.80 V across their plates. The two capacitors are not connected to anything else. The connecting wires are then reversed on the terminals of one capacitor, so that the positive plate of each capacitor is connected to the negative plate of the other capacitor.

a) Find the initial total charge stored.
I solved for it as if it was in parallel. I got 4.067e-5 C. This is correct.


(b) Find the final total charge stored.
I attempted to solve using it in series but I could not get the correct answer.


(c) Find the loss of electrical potential energy.


C=AEoK/d Eo represents Permitivvity and K is Kappa's constant of dialectrics



PLEASE PLEASE PLEASE HELP!!!
 

Answers and Replies

  • #2
tiny-tim
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hi thst1003! :smile:

(try using the X2 and X2 icons just above the Reply box :wink:)

if i'm understanding this correctly, you have charges +A and +B on the two connected plates on one side, and -A and -B on the other side

then you swap the wires so that +A and -B are connected (and -A and +B) …

so what happens to the charge? :wink:
 
  • #3
gneill
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Your 4.067E-5 number looks okay for the initial charge. You should also calculate the charge on the individual capacitors -- you'll need them later!

For part (b), one of the capacitors was inverted and reconnected. So if it had +++ charge on its top plate, and - - - on its bottom plate, that would now be reversed. What do you think will happen when the capacitors are connected in that orientation?
 

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