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Homework Help: Find the voltage potential and potential difference

  1. Sep 14, 2013 #1
    1. The problem statement, all variables and given/known data
    Three point charges Q1=1 mC, Q2=-2 mC, and Q3=3 mC are, respectively located at (0,0,4), (-2,5,1), and (3,-4,6)
    (a) Find the potential Vp at P(-1,1,2);
    (b) Calculate the potential difference Vpq if Q is (1,2,3)

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Sep 14, 2013 #2
    Your first line in part b) is correct, but the rest needs some re-thinking. You found the potential at P no problem, so why not do the same procedure for Q and then subtract the two, as you wrote down?
  4. Sep 14, 2013 #3
    Ok I redid it I get -685933.286 Volts
  5. Sep 16, 2013 #4
    Is my answer ok? Not trying to rush you I'm just wondering if it is ok?
  6. Sep 16, 2013 #5
    In general, I try to avoid telling people whether their numerical answers are correct. This is mainly because if I make the same calculator mistake you do, and tell you the answer is right, I'll feel super guilty when it comes back with red ink and you yell at me for misleading you ^^;

    If you follow the discussion on the physics that we talked about, any reasonable physics teacher should give you most if not all credit for doing the proper thinking. Make sure your units match up and you are doing everything in SI to correspond with your value for the k constant, and you should be good to go (you don't mention the units for the distance in your paper, so assuming meters, the order of magnitude looks ok).
  7. Sep 16, 2013 #6


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    Staff: Mentor

    ... also final results (for presentation as such) should have a reasonable number of significant figures, corresponding to those of the given data and any constants employed.
  8. Sep 16, 2013 #7
    ok thanks guys
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