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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.

Více

Anisotropní

Když je magnetický materiál natlačen do magnetického pole, nazývá se preferenčně orientovaným a anisotropním. Anisotropní materiál lze zmagnetizovat pouze v preferenční orientaci.