# Electrostatic force on the particle

1. Dec 25, 2006

### young physical

if a charged particle ic located inside a shell of uniform charge there is no net electrostatic force on the particle from the shell.
1st is this fact?
2nd if it is so plz explane it to because there is some distance between the particle and other chargeds in shell every one has different distance from anther?.

2. Dec 25, 2006

### Haywire

The electrostatic force is directly proportional to charge.
The electrostatic force is directly proportional to $1/r^2$.
But the charge is directly proportional to $r^2$.

3. Dec 25, 2006

### HallsofIvy

Staff Emeritus
Yes, it is a fact for spherical shells. For non-spherical shells it will be approximately true if the distance from the particle to the shell is large compared to the change in "radius" of the shell.

I have no idea what you mean by "every one has different distance". Isn't that always true?

Draw four straight lines from one side of the shell through the particle to the other side. The area of the shell contained within those four lines on one side offsets the area on the other side because, as Haywire said, the the ratio of the two areas is equal to the ratio of the distances squared, while the ratio of the forces due to the charge in each area is equal to the one over the ratio of the distances squared.