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## Homework Statement

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 +- [itex]\sigma[/itex]. Ignore edge effects and use Gauss's law to show

a) that for points far from the edges, the electric field between the plates is [itex]E = \frac{\sigma }{\varepsilon_0}[/itex].

b) that outside the plates on either side the field is zero.

c) How would your results be altered if two plates were nonconductors?

## Homework Equations

[itex]\phi = \oint E *dA = \frac{Q_(enc)}{\epsilon_0}[/itex]

## The Attempt at a Solution

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(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

[tex]EA = \frac{\sigma A}{\epsilon_0}[/tex]

[tex]E = \frac{\sigma }{\epsilon_0}[/tex]

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?