Magnetic hysteresis . In physics , for example, magnetic hysteresis is found if when magnetizing a ferromagnet it maintains the magnetic signal after removing the magnetic field that has induced it. The phenomenon can also be found in other electromagnetic behaviors, or elastic ones.
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- 1 Magnetic hysteresis
- 2 The hysteresis curve
- 3 Hysteresis cycle
- 4 Instrument for measuring the hysteresis cycle of a material
- 5 Hysteresis losses
- 6 Sources
It is the phenomenon that allows the storage of information in the magnets of the hard or flexible disks of computers: the field induces a magnetization in the small magnet, which is encoded as a 0 or a 1. This encoding remains in the absence of a field, and it can be read later, but it can also be inverted by applying a field in the opposite direction.
The hysteresis curve
The hysteresis curve shows the magnetization curve of a material. Whatever the specific material, the shape has similar characteristics.
- At first, magnetization requires a greater electrical effort. This interval is the so-called reversible zone.
- At a certain point, magnetization occurs proportionally. At this point the so-called linear zone begins.
- Finally, an instant comes when, no matter how much magnetic force we induce into the material, it is no longer magnetized. This is the so-called saturation induction point, which determines the start of the so-called saturation zone.
The figure represents the so-called HYSTERESIS CYCLE (also loop or hysteresis loop) of a certain magnetic material. A coil is supposedcreates on said magnetic material an intensity of field H, which induces in that magnetic material an induction of value B. Thus, an intensity of field H0 will correspond to an induction of value B0. If you now increase H (increasing the current flowing through the coil) to a value of H1, B will also increase to B1. But if we now return H to its initial value H0, B does not return to B0, but takes a different value B2. (Note that the path “to the go” is different from that “to the return”, which implies that to restore the induction in the nucleus to its primitive value, it is necessary to apply a supplementary current of opposite sign. Point S represents the saturation of the magnetic core. Once the nucleus is saturated, B cannot increase no matter how much H.
Instrument for measuring the hysteresis cycle of a material
In order to know the hysteresis cycle of a material, the Köpsel magnetometer can be used , which is responsible for providing the ferromagnetic material with the sinusoidal changes of the electric current to modify the direction of the magnets .
They represent a loss of energy that manifests itself in the form of heat in the magnetic nuclei. In order to minimize these losses, the cores are made of magnetic materials with special characteristics, such as silicon steel. The power loss is directly proportional to the area of the hysteresis curve.