# Surface charge concept

1. Jan 15, 2012

### SirBerr

First post,

I know that charges of the same sign repel one another and that will attempt to move as far away from one another as possible. Now, I'm reading my physics text book and it says charges will always move to the outer surface of a conductor even if the inner surface has a larger area. Think of a hollow sphere that has a pitted inner surface to give it more surface area than the outer.

Now why is this? My best guess is that because the electric field in a conductor is zero? What obvious thing am I missing here?

Thanks!

2. Jan 16, 2012

### Simon Bridge

Well if the charges were on the inside surface of a conductor, then they would be closer together wouldn't they?

It becomes clear if you consider how the inner surface area could possibly be bigger than the outer surface area.

3. Jan 16, 2012

### vivekrai

The logic however is not very convincing. Think in terms of potential and Electric field (and obviously using r1<r2)

4. Jan 16, 2012

### SirBerr

That makes slightly more sense now. I didn't consider the fields acorss the inner surface rather just the immediate surface around the charges. Not the clearest thing in the world but it makes a little bit more sense.

5. Jan 16, 2012

### Naty1

In addition, charges within a conductor will also move so as to create a zero field, a static condition, within the conductor.....you can tell this happens because if their were a net field then the charges would move in reaction to it.