hysterisis

Hysteresis is a phenomenon observed in a system where the state of the system depends on its history. This means that the output of a system is not solely determined by its current input, but also by the sequence of past inputs it has experienced. When the input is varied, the system's response follows a path, and when the input is reversed, the system does not retrace the exact same path. This creates a loop in a plot of the system's output versus its input.

The term hysteresis comes from the Greek word "hysterēsis," meaning "lagging behind." It is observed in various scientific and engineering fields. In physics, hysteresis is commonly seen in magnetic materials. When a magnetic field is applied to a ferromagnetic material, it becomes magnetized. As the applied field is removed and then reversed, the magnetization does not immediately follow the applied field but lags behind, forming a hysteresis loop.

This phenomenon also appears in other areas. In electrical engineering, hysteresis is found in components like relays and Schmitt triggers, where it is used to prevent chattering or oscillations. In economics, hysteresis can describe how unemployment rates can remain high even after a recession ends, as former workers lose skills or become discouraged. In biology, hysteresis can be observed in cellular processes or physiological responses where past stimuli influence current reactions. The presence of hysteresis implies that a system has some form of memory.