A law in classical electromagnetism and Newtonian gravity which relates (charge) density to the divergence of a field, or alternatively the charge in a volume to the flux through the bounding surface.
A law in Classical Electromagnetism and Newtonian Gravity.
Understanding Gauss's law
Classical Electromagnetism
Classical Electricity
Gauss's law for Electricity states that:
$$\nabla\cdot\vec E=\frac{q}{\epsilon_0}$$
Classical Magnetism
Gauss's law for Magnetism states that:
$$\nabla\cdot\vec B=0$$
Newtonian Gravity
Gauss's law for Gravity is simply Poisson's equation
$$\nabla\cdot\vec E=4\pi G\rho$$