Exchange spring magnet
The magnetostatic energy is the energy stored in the field generated by a material's magnetic moments. The magnet's field reaches its maximum intensity if all the magnetic moments orient in one direction; this is what occurs in a hard magnet. In order to prevent building up the magnetic field, sometimes magnetic moments tend to form loops. That way, the energy stored in the magnetic field can be constrained; this is what occurs in a soft magnet. What determines whether a magnet is hard or soft is the dominant term of its magnetic energy. For hard magnets, the anisotropy constant is relatively large, making the magnetic moments align with easy axis. The opposite case applies to soft magnets, in which the magnetostatic energy is dominant.
Magnetic level gauge
Exploring the physics and engineering behind this design, requires looking at basic magnetism. A standard bar magnet has two magnetic poles: north and south. (The north will read positive on a gauss meter and the south will read negative.) Magnetic field are mapped using magnetic flux lines. These lines are a graphical representation of the magnetic field density. They show the direction of flow for the magnetic field and represent relative field strength – the closer together the lines are, the stronger the magnetic field. Flux lines will always travel from the north pole to the nearest south pole and always leave and enter surfaces at 90°, or perpendicular to the surface. They can only travel in straight lines or curved paths, which means they can never make a sudden, abrupt change in direction. Flux lines will also always follow a path of least magnetic resistance. Most importantly, they can never cross one another.