Magnetic fields are perhaps more easily understood in terms of magnetic field lines. Field lines , also known as lines of force , define the direction and strength of the magnetic field at any local in space. The direction of the field lines indicates the direction of the field, while the density of the field lines indicates the magnitude of the field. Thus at points where the field lines are closer together, the field is stronger. Field lines are described mathematically with a quantity known as flux .
Magnetic fields are commonly a result of magnetic dipoles .
This diagram illustrates the magnetic field lines of a typical magnetic dipole. Magnetic dipoles always like to align themselves parallel to an external magnetic field, so the dipole's field matches the one applied to it. The north pole of a magnet is the pole that aligns itself with geographic north. To identify the north pole of a magnet, you can make a compass out of it. Either hang it on a string or float it on water.