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(Ferro) magnetism

Back in ancient times, people discovered that magnetite crystals attract or repel each other depending on their orientation. This physical phenomenon is referred to as magnetism. The words magnetite and magnesium are both derived from Magnesia, the name of an area in the Thessaly region of Greece where magnetic stone can be found in abundance.Magnetic separation

It is the iron in the rock that is responsible for the magnetic properties of magnetite. Many iron alloys possess magnetic properties. In addition to iron, we find magnetic properties in nickel, cobalt and gadolinium as well.

Although ferromagnetic (and ferrimagnetic) materials are the only kinds with strong enough magnetic properties to be drawn to a magnet (which is why they are called ‘magnetic’), all other substances also respond weakly to a magnetic field, via one or more other types of magnetism.

Ferromagnetic materials can be divided into magnetically 'soft' materials, such as annealed iron, which can be magnetized but usually do not retain the magnetization indefinitely, and magnetically 'hard' materials that do remain magnetized. Permanent magnets are made of 'hard' ferromagnetic materials such as Alnico and ferrite, which undergo special processing in a powerful magnetic field during production to 'align' their internal microcrystalline structure, making them very resistant to demagnetization.

Objects which strongly exhibit this behaviour are called magnets. There are natural and man-made magnets (e.g. Alnico, Fernico, ferrites). All magnets have two poles, which are referred to as the north pole and the south pole. The north pole of a magnet repels the north pole of other magnets and attracts the south pole of other magnets. Two south poles also repel.

Magnetism Gripper

Because the earth has a magnetic field as well, with its magnetic south pole close to the geographic north pole and its magnetic north pole close to the geographic south pole, a free-spinning magnet will always take on a north-south orientation. The names of the poles of a magnet are derived from this phenomenon. For the sake of convenience, but nevertheless slightly confusing, the south pole of “the 'earth magnet' is called the magnetic north pole and the north pole of the 'earth magnet' is called the magnetic south pole.

Magnetic field - North and South pole

A related phenomenon is electromagnetism, which is magnetism generated by an electric current. In essence, all magnetism is caused by either rotating or revolving electrical charges in eddy currents.


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Fluxdichtheid (Magnetische fluxdichtheid) B

De fluxdichtheid, ook met de verouderde term magnetische inductie aangeduid, is de hoeveelheid magnetische veldlijnen die op een bepaald punt door een oppervlak lopen. De SI-eenheid is T (tesla), dat is weber per vierkante meter (Wb/m2) en de eenheid in het CGS-systeem is G (gauss). 1 tesla is gelijk aan 10.000 gauss.

Magnetische fluxdichtheid wordt in formules doorgaans aangeduid met het symbool , een (pseudo) vectorveld.

In een punt van een magnetisch veld is de magnetische fluxdichtheid voor te stellen als een vector in de veldrichting met een grootte gelijk aan de "lorentzkracht" die een stroomdraad per meter en per ampère ondervindt als de stroomdraad loodrecht op de veldlijnen staat.

Hoe hoger de fluxdichtheid, des te sterker de magneet op dat punt is, en des te beter hij op dit punt ijzerdeeltjes kan vasthouden.

Goudsmit kan de fluxdichtheid berekenen met de Eindige Elementen Methode (FEM berekening). Dit zorgt ervoor dat we sneller en beter de juiste magneet kunnen ontwikkelen voor een nieuw of bestaand product of toepassing. Hier leest u meer over magneetberekeningen.

Magnet materials


Ferrite magnets Read more

Neodymium (Neoflux®) magnets

Neodymium Neoflux Magneten Read more

Samarium-cobalt magnets

Samarium Kobalt magneten Read more

Aluminum-nickel-cobalt magnets

Aluminum-nickel-cobalt magnets Read more

Plastic bonded magnets

Plastic bonded magnets Read more