# Does the use the use of ε0 imply that it is for vacuum?

1. Jun 5, 2014

### ugenetic

I found most literatures on Electrical or Magnetic fluxes maddeningly unclear about the MATERIAL in which the equations are applied. In free air only? or not?

I would like to know if the following 2 statements are true
the electrical flux generated by a single charge will look the same in all (uniform) materials.
the electrical field E generated by a single charge will change from one material to another depends on εr.

I m guessing maxwell equations are really for conductors and air?

2. Jun 5, 2014

### Simon Bridge

$\epsilon_0$ is for a vacuum. It is often used as an approximation in air since the relative permativity of air is very nearly 1.

You should be able to tell whether a vacuum is intended or not by the context.

Maxwels equations are for everywhere.
Some people just write them out for the vacuum case.

3. Jun 6, 2014

### Staff: Mentor

In a formula, εo is always accompanied by εr.

Similarly, μo is always accompanied by μr.

If the relative constant is not explicitly shown, it is taken as unity (meaning its value in free space).

4. Jun 6, 2014

### Baluncore

The electric flux distribution will be the same for any one isotropic material only if the boundary conditions are perfect conductors and/or insulators, and the geometry is fixed.

5. Jun 6, 2014

### ugenetic

OH WOW, so clear, thank you all. I am writing them down.

Last edited: Jun 6, 2014