Hystereesisähviöihin

Hystereesisähviöihin, often translated as hysteresis loop or magnetic hysteresis, refers to the phenomenon observed in ferromagnetic materials where the magnetization of the material does not immediately follow the changes in the applied magnetic field. Instead, it lags behind, creating a loop when the magnetic field is cycled. This lag is due to the irreversible movement of magnetic domain walls within the material.

When an external magnetic field is applied to a demagnetized ferromagnetic material, the magnetic domains align with the field, causing an increase in magnetization. As the field is increased further, the material becomes saturated, meaning all domains are aligned, and further increases in the field do not increase the magnetization significantly. However, when the external field is reduced, the magnetization does not return to zero along the same path. A certain amount of residual magnetism, known as remanence, remains. To reduce the magnetization to zero, a reverse magnetic field, called the coercive field, must be applied.

Continuing to increase the magnetic field in the reverse direction will eventually lead to saturation in the opposite direction. Cycling the magnetic field back and forth between positive and negative saturation points traces out a characteristic hysteresis loop. The area enclosed by this loop represents the energy lost as heat during each cycle of magnetization and demagnetization.

The shape and size of the hysteresis loop are important characteristics of magnetic materials. Soft magnetic materials, used in transformers and inductors, have narrow hysteresis loops with low coercivity, indicating low energy loss and easy magnetization and demagnetization. Hard magnetic materials, used in permanent magnets, have wide hysteresis loops with high coercivity, meaning they retain their magnetism strongly and resist demagnetization. Hystereesisähviöihin is a fundamental concept in understanding and designing magnetic devices.