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Homework Help: Magnitude of the work done by electric field.

  1. Feb 14, 2017 #1
    1. The problem statement, all variables and given/known data
    The membrane around a cell normally has layers of charge that create a potential difference between its outer and inner surfaces. This difference is about 72 mV .

    When a singly ionized potassium ion moves through a channel in the membrane passing from the outside to the inside, what is the magnitude of the work done by the electric field of the membrane?


    2. Relevant equations
    W = F*d
    W = V*U

    3. The attempt at a solution
    So I know that the charge of a K ion is +1 so it is simply 1.6e-19 and converting 72 mV to 0.072 V I can then just multiply both to get the change in work correct? I don't get why that is wrong then.
  2. jcsd
  3. Feb 14, 2017 #2


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    2017 Award

    Staff: Mentor

    Just a multiplication error.
    Quick check: If you multiply 1.6*10-19 by 0.072, the result should be smaller than 10-19.
  4. Feb 14, 2017 #3
    Yeah I keep getting 1.15e-19. Isn't that correct, I cant seem to get a different answer on my calculator. Nevermind I got the answer. I was using -18 instead of -19.
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