Hystereesisäkäyrä

Hystereesisäkäyrä, commonly known as a hysteresis loop, is a graphical representation illustrating the relationship between a changing magnetic field and the magnetization of a ferromagnetic material. It depicts how the magnetic flux density within a material lags behind the applied magnetic field strength. When the magnetic field is first applied, the magnetic domains within the material align, causing an increase in magnetization. As the field strength increases, the material eventually saturates, meaning it can no longer become more magnetized. When the field is then reduced, the magnetization does not return to zero along the original path. Instead, it retains a certain level of residual magnetism, known as remanence. To demagnetize the material completely, a reverse magnetic field must be applied, known as the coercive force. Further increasing the reverse field leads to saturation in the opposite direction. When the field is returned to zero and then increased in the original direction again, the cycle repeats, forming a closed loop. The area enclosed by the hysteresis loop is proportional to the energy lost as heat during each magnetization cycle, which is a significant factor in applications involving AC magnetic fields. Different ferromagnetic materials exhibit different hysteresis loop shapes, which are crucial for selecting materials for specific applications such as permanent magnets, transformers, and magnetic recording media.