# B Charge on a conducting shell

1. Apr 29, 2017

### pixel

It’s been a long time since I took E&M courses and even thought about these things, but a current thread has led me to question the location of excess charge on a conducting shell. Given that there are two surfaces to which charge can move, why doesn’t some charge also locate on the inner surface? Other than that it is on the outside, what makes the outer surface different from the inner surface as far as determining where charge locates?

I know from Gauss’s Law that the charge must be on the outer surface. I’m just looking for a physical/intuitive reason, hence the B prefix on this thread.

2. Apr 29, 2017

### Staff: Mentor

Intuitive reason? Imagine that we were to place charged particles on the inner surface in such a way that there was a uniform charge density on the inner surface. The charged particles would all be repelling one another, so they would experience a net outwards force... And that pushes them to the outer surface.

3. Apr 30, 2017

### pixel

Yes, so charge can't just be on inner surface. But couldn't we still consider charge on both the inner and outer surfaces such that the mutual repulsion was keeping them separated?

4. Apr 30, 2017

### Staff: Mentor

You won't get any repulsion unless there is a non-zero electrical field. All points on the interior surface are inside of the uniform spherical distribution of charge on the exterior surface. What is the electrical field inside of a uniform spherical charge distribution?