# Gauss's law:E vs r graph (two cases of shell)

1. Sep 21, 2015

### gracy

1. The problem statement, all variables and given/known data
Ok.Then there was a question
If r is distance measured from center of a charged shell and R is it's radius then the graph which may correctly represent variations of electric field is

2. Relevant equations
E vs R graph

3. The attempt at a solution
The answer is given to be A but I want to ask why not C ?There are two cases
1-shell with all charges on surface in this case E for r<R is zero so Option A fits in
2-Shell with charges throughout the volume(volumetric distribution)
In which E for r<R has formula
E=ρr/3ε0 (ρ=CHARGE PER UNIT VOLUME)
it is clear E ∝ r
For this C seems correct.And the question does not clarify which type of shell(type 1 or type 2) is to be referred
So why answer is A?Why it can't be C?

2. Sep 21, 2015

### blue_leaf77

"Shell" is usually intended to mean an infinitesimal (limit-zero thickness) surface.

3. Sep 21, 2015

### gracy

so no volume ?nearly 2d?

4. Sep 21, 2015

### blue_leaf77

Yeah, no volume. The shell alone has no volume, but of course it encompasses certain volume inside it.