Histereesilmukka

Histereesilmukka, often translated as hysteresis loop, is a graphical representation of the relationship between a material's magnetic flux density and the applied magnetic field strength. It illustrates how a ferromagnetic material's magnetization lags behind changes in the applied magnetic field. When a magnetic field is applied to a previously unmagnetized ferromagnetic material, the magnetic domains within the material align themselves with the external field. As the field strength increases, more domains align, leading to an increase in magnetic flux density.

When the applied magnetic field is removed, the magnetic flux density does not return to zero. Instead, it retains a residual magnetism, known as remanence. To bring the flux density back to zero, a reverse magnetic field, called the coercive field, must be applied. This phenomenon of lagging response is hysteresis.

The area enclosed by the hysteresis loop represents the energy lost as heat during each cycle of magnetization and demagnetization. Materials with narrow hysteresis loops are considered magnetically soft and are easily magnetized and demagnetized, making them suitable for applications like transformer cores and electromagnets. Materials with wide hysteresis loops are magnetically hard and retain their magnetism strongly, making them useful for permanent magnets. The shape and size of the hysteresis loop are characteristic of the specific ferromagnetic material and its properties.