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Electricity capacitor

  1. Dec 15, 2012 #1
    1. The problem statement, all variables and given/known data

    A proton just floating in a field in a between two boards (g=9,82 m/s^2)
    What is the voltage U?

    distance d = 2 m
    charge for protone Q = 1,602*10^-19


    2. Relevant equations

    E = F/Q

    E = U/d


    3. The attempt at a solution

    I've tried two different ways of which I don't know is correct
    In both cases I assume that F = 9,82 as something must be lifting it upp to make up for the gravitation

    Attempt 1.

    F = g = 9,82

    E = F/Q = 9,82/(1,602*10^-19) = 6,13

    E = U/d --> U = E*d = 6,13*2 = 2,26 V

    Attempt 2.

    E = U/d --> U = E*d = 19,64 V
     
    Last edited: Dec 15, 2012
  2. jcsd
  3. Dec 15, 2012 #2

    gneill

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    Staff: Mentor

    Careful, you're using g (acceleration due to gravity) as a force. The force due to gravity on the proton would be its weight, m*g.
     
  4. Dec 15, 2012 #3
    Oh, I forgot about that
    Probably not the right solution considering the answer:

    F = m*g = 1,672*10^-27 * 9,82 = 1,642 * 10^-26

    E = F/Q = (1,672*10^-26)/(1,602*10^-19) = 1,044*10^-7

    E = U/d --> U = E*d = (1,044*10^-7)*2 = 2,088*10^-7
     
    Last edited: Dec 15, 2012
  5. Dec 15, 2012 #4

    gneill

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    Staff: Mentor

    Looks okay to me.
     
  6. Dec 16, 2012 #5
    Okay, thank you for the help :smile:
     
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