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Homework Help: 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

    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.

    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


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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
  4. Sep 29, 2011 #3
    Thanks a lot! That really helps!
  5. Sep 29, 2011 #4


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