Question

Gauss's Law anyone?

Answer 1

A very large (infinite), uniformly charged slab of plastic of thickness 2a occupies the region between the z=-a plane and the z=+a plane.

Answer 2

In the problem they drew an object in the shape of a can, why do we assume that that's the shape?

Answer 3

I meant to say "In the solution"

Answer 4

It further says Find the Electric field everywhere due to this charge configuration. The charge per unit volume is \[\rho\]
The solution is
\[\vec{E}=E_z\hat{k}=\]
and then it gives us a piecewise solution I can write them all out if you want me to

Answer 5

The crux of the argument is that the only possible orientation of the electric field is toward or away from the plate. That is, there can be no component other than either up or down. Do you understand why that is?

Answer 6

I don't quite understand it.
Wouldn't the electric field point away from that slab of plastic? To the right and left

Answer 7

Oh, I apologize, I misread the question. Yes, left and right. So that's clear, then?

Answer 8

uhm yes. but why do we assume that the shape is the following?
It's supposed to look like a symmetrically shaped can.

Answer 9

What you're trying to do is to use the symmetry argument to determine the electric field strength. A "can" shape is a good choice because the only contribution to the electric flux is through the top and bottom of the can. The sides don't contribute, because the electric field is tangential to them.

Answer 10

So the total flux is equal to the flux through the top of the can plus the flux through the bottom: