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Electric Potential Energy of a Cube of 8 protons

  1. Sep 29, 2011 #1
    1. The problem statement, all variables and given/known data

    Suppose we there is a cube (a x a x a) made up of 8 protons. 1 at each point
    What is the Electric Potential Energy


    2. Relevant equations
    U=q1*q1/4*pi*epsilon_0*r



    3. The attempt at a solution
    *U12 = Potential Energy to bring 2 to 1*
    I'm aware of how to do the question but I'm not sure if I'm expressing it correctly. Remember that the potential energy is the work done configure this system in space.
    W1=0
    W2=U12
    W3=U12+U13
    W4=W3+U14
    W5=W4+U15
    W6=W5+U16
    W7=W6+U17
    W8=W7+U18

    Then the Electric Potential Energy would be = Wtotal = W1+W2 . . . + W8

    I am also aware that when I show my equation fully that some of the distances will be sqrt(2a^2)
     
  2. jcsd
  3. Sep 29, 2011 #2

    Redbelly98

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    The work to bring in the 3rd charge is U13 + U23
    And for the 4th charge it's U14 + U24 + U34
    Yes.
     
  4. Sep 29, 2011 #3
    Thanks a lot! That really helps!
     
  5. Sep 29, 2011 #4

    SammyS

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    Some pairs of protons have a separation distance of (√3)a .
     
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