# Effect of media on electric force

1. Jul 22, 2013

### Gavroy

I was thinking about the following: Assuming that you have NON SPHERICALLY SYMMETRIC charges and they are both in medium 1. Does it make a difference(whereby I am referring to the total force between these two charges) if there is a second medium 2 in the local area of both? So both charges are in medium 1 and there is a medium 2 where some electrical field lines go trough? Does this have any effect on the force if there is another medium where field lines go through?

2. Jul 23, 2013

### Simon Bridge

Set up a specific situation and apply Gauss' Law or Poisson's equation and see.
Is there a special reason the charges need to be non-spherically-symmetric?

3. Jul 23, 2013

### Gavroy

So no, it does not change anything right?

4. Jul 23, 2013

### Simon Bridge

You should do the math :)

Put two charges separated by distance r in medium with relative permittivity $\epsilon_r$ while there is an empty region nearby.

5. Jul 23, 2013

### Gavroy

but if I take the surface(in Gauss law) such that there are only electric field lines, that are in medium 1, then it does not matter that there is another medium, right? So the electric field is the same. I would thank you if you could confirm this idea, somehow.

6. Jul 24, 2013

### Simon Bridge

That's the idea - the force on charge 2 due to charge 1 depends on the charge enclosed by the Gaussian surface and the medium charge 2 is in. At this level, everything is decided locally. That's the advantage of the electric field model - pretty soon you will use electric force less and less and do more and more physics using fields.

(Also look at what happens when the charges are in different media.)

Your reasoning is not bad - you should be able to figure stuff out more confidently with a bit of practice - hint: most of physics is just asking useful questions.

Don't forget the "thanks" button :)