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Homework Help: Work on Electricity (is this right?)

  1. May 1, 2010 #1
    1. The problem statement, all variables and given/known data
    Four identical point charges (+4.0 mC) are placed at the
    corners of a square which has 20-cm sides. How much work is required to
    assemble this charge arrangement starting with each of the charges a very large
    distance from any of the other charges?

    3. The attempt at a solution
    I want to know if this is the right formula and answer:

    U=K(q1q2/r12 + q1q3/r13 + q1q4/r14 + q2q3/r23 + q2q4/r24 + q3q4/r34)
    i got 3.9 as the answer.
  2. jcsd
  3. May 1, 2010 #2


    User Avatar

    Staff: Mentor

    Looks like a reasonable approach to me. You should get in the habit of putting units on at least the answer, though.
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