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Electromagnetism

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current.

They are often used instead of permanent magnets when a deep and strong magnetic field is necessary. Another main advantage of an electromagnet over a permanent magnet is that the magnetic field can be turned off, or quickly changed by controlling the amount of electric current in the winding.

In general, electromagnets consist of a core of magnetic or ferromagnetic material, such as soft iron, around which a coil has been wound. As long as an electric current flows through the coil, the core remains magnetic.

pot magnets electro-magnetic
Electro-magnet large

 

Working principle

A magnetic field is generated around a conductive wire through which an electric current flows. The generated magnetic flux density B is expressed in tesla (T), gauss (G = Vs/m2) or weber (Wb/m2):

Electromagnetism

Φ = L * I

B = ΔΦ/ΔS   , with ΔS in [m2].

where:

Φ   is the magnetic flux expressed in weber (Wb)
L    is the self induction in henry (H)
I     is the current in ampère (A)

A strong magnetic field is obtained with high current or large self-induction. High currents are not always feasible or desirable (danger, heat production), which is why a high self-induction is usually utilized, obtained by winding a wire into a coil shape, referred to as a 'solenoid'. The fields generated in each winding act collectively, resulting in a strong magnetic field.

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Terminologie

Anisotrope

Lorsqu'un matériau magnétique est comprimé dans un champ magnétique, on dit qu'il a une préférence d'orientation, qu'il est anisotrope. La magnétisation d'un matériau magnétique anisotrope ne peut avoir lieu que dans l'orientation de préférence.

Matériaux magnétiques

Aimants
Ferrite
 

Aimants Ferrite En savoir plus

Aimants Néodyme (Neoflux®)

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Aimants Samarium-Cobalt

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Aimants Aluminum-Nickel-Cobalt

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Aimants à liant plastique
 

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