Hysteres

Hysteresis is a phenomenon where the state of a system depends on its history. It is observed in various physical and biological systems. In magnetism, a ferromagnetic material exhibits hysteresis, meaning its magnetization depends not only on the current applied magnetic field but also on the field that was previously applied. This is often visualized by a hysteresis loop, which plots magnetization against magnetic field strength. As the magnetic field is increased and then decreased, the magnetization does not follow the same path, creating a loop.

In other contexts, hysteresis can describe the lag between an input and its corresponding output. For example, in some biological systems, a particular stimulus might be required to initiate a response, and once initiated, the response may persist even after the stimulus is removed. Similarly, in economics, hysteresis can refer to persistent effects of temporary shocks, such as unemployment rates remaining high long after an initial recession has ended. The key characteristic of hysteresis is the memory effect, where past conditions influence the present state of the system. This often leads to different outcomes depending on the direction of change or the path taken.