# Electrostatics - Charge Density

1. Nov 5, 2008

### Herbststurm

Hi,

if we only have an electrostatic potential given. How to calculate the charge density?

I know of course Maxwell equation, here without any time dependence, but I missed always some further specifications, or I forget something important

thanks
greetings

2. Nov 5, 2008

### Ben Niehoff

Use Laplace's equation (derived from Gauss's Law):

$$-\nabla^2 \Phi = \rho / \epsilon_0$$

3. Nov 5, 2008

### clem

That's Poisson, not Laplace.

4. Nov 6, 2008

### Herbststurm

Thanks, that helps a lot.

I knew Poissons equation, but I forgot it. Damn... :grumpy:

Greetings