Electric Potential Difference Created by Point Charges

1. Feb 16, 2006

BoogieL80

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. Feb 16, 2006

durt

The charge to the top left is farther away than the others.

3. Feb 16, 2006

150grainhunter

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.