Finding the potential difference?

  • Thread starter Simon316
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  • #1
Simon316
7
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okey the question goes like this

A plate capacitor with area A and distance d1 is charged to a potential difference of V1 between the plates. Now the distance between the plates increases to d2 = 2*d1.

a) What is the new potential difference, V2, between the plates?

b) Find the increase in stored energy, deltaU, an explain where this energy comes frome.

what I have found out so far is:
a) V2 = E*2*d1, where E = Q/(e0*A) and therefore does not change with distance.

b) deltaU = 1/2*Q*V2 - 1/2*Q*V1


I don't think these two answers are good enough, but I can't se what else to do, maybe use intgral?
any help is highly appreciated:smile:

Kind regards

Simon
 

Answers and Replies

  • #2
denverdoc
963
0
Simon,

using your eqn a) what is the ratio v2/v1?
 
  • #3
Simon316
7
0
well the ratio must be V2/V1 = d1, but this can't be the answer to a) could it?
 
  • #4
denverdoc
963
0
unless I miss my guess, it should be 2di/di=2.
 
  • #5
Simon316
7
0
hehe yea ofcorse:smile:
but I still don't think the ration is the answer to thequstion, thanks though:smile:
 

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