Field lines / Lines of force

Magnetic field lines run outside a magnet from the north pole to the south pole and inside a magnet in reverse. They never intersect. The density of the magnetic field lines represents the strength of the magnetic field, also defined as flux density.

In a homogeneous magnetic field, the strength and direction of the field is the same everywhere. This is the case, for example, with horseshoe magnets. In an inhomogeneous magnetic field, the magnetic force of one pole is greater than that of the other, causing particles to be deflected.

Magnetic field lines become visible by placing a sheet of paper on a magnet and sprinkling some iron filings on it. The iron filings will cluster along the field lines therefore showing them. A compass needle also points in the direction of the field lines, so you can also follow them that way.