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Electrical Work Help!

  1. Feb 5, 2009 #1
    Hi there. I was attempting this problem but my answer is not agreeing with my friends.
    He got 1.4 *10^-7
    Any help will be appreciated.
    1. The problem statement, all variables and given/known data
    Calculate the work done on a system if its voltage drops from 15 V to 5 V.
    edge length= 1 cm
    water permittivity e=78.54e


    2. Relevant equations

    dwelec = (elec pot.)dQ
    Q=(elec pot)2ed
    e=78.54 * eo

    3. The attempt at a solution
    w = (elec pot.)f (Qf - Qi)
    =(elec pot.)f (2ed)[(elec pot.)f - (elec pot.)i]
    =(5V)(2(78.54)(8.854*10^-12)(0.001)(5V-15V)
    = -6.954 * 10^-11 J
     
  2. jcsd
  3. Feb 5, 2009 #2

    Borek

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    Staff: Mentor

    What is the system in question?
     
  4. Feb 5, 2009 #3
    its an hypothetical electrochemical cell.
     
  5. Feb 5, 2009 #4

    Borek

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    Staff: Mentor

    Geometry? Edge length of 1 cm can be appliead to anything.
     
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