Potential difference problem

1. Feb 15, 2005

jordanl122

Two parallel plates having charges of equal magnitude but opposite sign are separated by .12 m. Each plate has a surface charge density of 36 nC/m^2. Determine the potential difference between the plates.

I have to admit I am at a bit of a loss on how to answer this
(lettings S represent the integral sign)
I know Delta V = -SEds
and that E is constant so
Delta V = -ESds so delat V = -Ed
but I am not sure how to find E, I know sigma =Q/A
and I dont see how Gauss' law could really work here

any light someone can shed would be greatly appreciated.

2. Feb 15, 2005

vsage

Pretty classic problem. Assume the plate is infinite and make a cylindrical gaussian surface whose length is perpendicular to the face of a sheet: Illustrated in better detail here

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elesht.html#c2 Just remember that through the top and bottom of the cylinder flux equal to EA comes out, so the total flux is 2EA.