Hysteresisilmiöitä

Hysteresisilmiöitä refers to a phenomenon where the response of a system to a stimulus depends not only on the current stimulus but also on its past history. This means that if the stimulus is increased and then decreased, the system's output will not follow the exact same path. The difference between the increasing and decreasing paths is known as hysteresis.

Hysteresis is commonly observed in magnetic materials. When a magnetic field is applied to a ferromagnetic material, it becomes magnetized. As the magnetic field is increased, the magnetization also increases. However, when the magnetic field is decreased, the magnetization does not decrease along the same curve. Some residual magnetization remains even when the external field is zero. This residual magnetism is known as remanence. To demagnetize the material completely, a reverse magnetic field must be applied, which is called the coercivity. The graphical representation of magnetization versus applied magnetic field for a ferromagnetic material is called a hysteresis loop.

This phenomenon is not limited to magnetism. It also occurs in other physical systems, such as ferroelectric materials, mechanical systems (e.g., rubber elasticity), and even in economic and biological contexts. For example, in economics, hysteresis can describe how unemployment can have long-term effects on the labor market, even after the initial shock that caused the unemployment has passed. In biology, it can be seen in how certain physiological responses can be slower to reverse than to initiate. The presence of hysteresis signifies that a system has a "memory" of its past states, influencing its future behavior. Understanding hysteresis is crucial for designing and predicting the behavior of many technological devices and for analyzing complex systems.