Gauss Law for Magnetism

When you break a magnet, both pieces have a north pole and a south pole. Unlike charge, you cannot isolate a single pole (no magnetic monopoles). This means that the magnetic field lines close upon themselves.

Whatever magnetic field lines leave the closed surface will enter the closed surface somewhere else. This is represented mathematically:

$\oint \vec{B}\cdot \overrightarrow{dS}=0$

title: Quantum World
In the [[Quantum Physics]] world, there needs at least one magnetic monopole somewhere in the universe for the chrage to be quantized. 
 
However, we haven't found them yet.