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Homework Help: Electric Potential Difference Created by Point Charges

  1. Feb 16, 2006 #1
    I'm working on the following problem:

    The drawing shows four point charges. The value of q is 2.0 µC, and the distance d is 0.74 m. Find the total potential at the location P. Assume that the potential of a point charge is zero at infinity.

    http://www.boomspeed.com/boogiel80/physics19.3.gif [Broken]

    I converted my charge to 2.0e-6. I used the formula V= kq / r and came up with values of -2.43e4 for each of the parallel charges and the same numbers, only positive, for each of the perpendicular charges. I assumed I was suppose to add all the charges and I got a total of 0 V. However, webassign is saying that is the incorrect answer. Any input would be nice.
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Feb 16, 2006 #2
    The charge to the top left is farther away than the others.
  4. Feb 16, 2006 #3
    Alright I'm learning the same stuff right now so I should be able to help. The thing to remember is that these are not to be added as vectors. The positive charge q that is a distance d from point p will cancel out one of the -q charges that is a distance d from point p. So you will need to find the potential due to the positive charge q that is a distance 2d away from point p and the potential due to the -q charge that is a distance d from the point p. Add these together and you should get your answer.
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