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What is hysteresis?
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What is hysteresis?
Hysteresis is a phenomenon whereby the value assumed by a quantity dependent on others is determined not only by the instantaneous values of the latter, but also by the values they had assumed previously; in other words, hysteresis is the characteristic of a system to react in delay to applied stresses and in dependence on the previous state. The term, derived from the Greek ὑστέρησις (hystéresis, “delay”), was introduced in the modern sense by James Alfred Ewing in 1890, and is used generally in the theory of dynamical systems, thus not only in physics, but also in biology and economics.
If the response of a system with hysteresis is plotted in a graph as a function of stimulus, a characteristic closed curve is obtained. In a system without hysteresis, the curve forms a single line.
In the presence of hysteresis you get a splitting of the curve: if traveled from left to right you have a path, if traveled in the opposite direction you get another. In many of the physical phenomena in which we have this characteristic we obtain two horizontal lines: one upper and one lower. These represent the saturation limits.
For a system under consideration, as certain conditions vary, one can have a family of curves, ranging from nearly single to a nearly square enclosed area. The amplitude of the enclosed curve is an indication of the magnitude of the hysteresis. The families of curves can be arranged in the third dimension to delimit a three-dimensional shape.
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