Hystereesiilmiöitä

Hystereesiilmiöitä, known in English as hysteresis phenomena, refers to a property of some physical systems where the state of the system depends not only on the current input but also on its past history. This means that the output of the system will not follow the same path when a quantity is increased as it does when that quantity is decreased. Instead, a loop is formed on a graph plotting the input against the output.

This effect is observed in various fields. In magnetism, ferromagnetic materials exhibit magnetic hysteresis, where the magnetization of the material lags behind the applied magnetic field. This is crucial for the operation of permanent magnets and magnetic storage devices. In materials science, stress-strain curves often show hysteresis, particularly in the plastic deformation region, indicating energy loss during loading and unloading cycles. Dielectric hysteresis is seen in ferroelectric materials, where the electric polarization lags behind the applied electric field.

In economics, hysteresis can describe situations where temporary shocks have permanent effects on economic variables like unemployment. For example, a recession might lead to a structural increase in long-term unemployment that persists even after the economy recovers. The presence of hysteresis implies a memory effect within the system, making its behavior path-dependent and potentially more complex to predict and control. Understanding hysteresis is vital for accurate modeling and design in many scientific and engineering disciplines.