Two large, flat metal plates are separated by a distance that is very small compared to their height and width. The conductors are given equal but opposite uniform surface charge densities +- $\sigma$. Ignore edge effects and use Gauss's law to show that for points far from the edges, the electric field between the plates is $E = > \frac{\sigma }{\epsilon_0}$.
I've searched a lot to find a solution to this problem.
http://aerostudents.com/files/physics/solutionsManualPhysics/PSE4_ISM_Ch22.pdf (solution number 24) http://www.phys.utk.edu/courses/Spring 2007/Physics231/chapter22.pdf (page 21)
In both of these links, the approach to find electrical field between the plates is
1- create a cylindrical gaussian surface
2- put one end of the cylinder to one of the plates where the area is uncharged (uncharged due to attraction between two plates)
3- put other end to be between the plates.
Since the flux will pass through only one end of this cylinder
$$EA = \frac{\sigma A}{\epsilon_0}$$ $$E = \frac{\sigma }{\epsilon_0}$$
My question is, why didn't we do the same thing for the other plate, and then use superposition principle? Or simply, why didn't we multiply what we found by 2 because of superposition?
because of superposition
. $\endgroup$ – Steeven Mar 8 '15 at 16:33