Hysteresis

That is to say a size causes noted C producing a size effect noted E. One says that there is hysteresis when the curve E = F (C) obtained with the growth of C is not superimposed with the curve E = F (C) obtained with the decrease of C. Generally, the reason is that the variations of E are done with a certain delay compared to those of C, this producing delay of discontinuities during the inversions of the variation of C.

When one imposes on the cause C periodic variations, hysteresis is responsible for a particular form for the curve E = F (C) called hysteresis loop .

Note: these curves are only possible forms of a phenomenon of hysteresis. The cycle can not be centered around the item (0; 0) if the periodic variation of C is not symmetrical compared to the origin.

Remarks

The phenomena of hysteresis are responsible for the appearance of nonLinéarité S in the relation E = F (C) sometimes making very difficult modeling of this relation by a mathematical equation.

The phenomenon of hysteresis can have advantages. For example for the temperature controls by Thermostat, one introduces hysteresis into the order so that the instruction of temperature for lighting is different from the instruction for the stop. This makes it possible to avoid too many starting or extinction of the boiler. The comparators fulfilling this function are called comparators with hysteresis .

One also finds a phenomenon of hysteresis in the cycles of magnetization and demagnetization: cf Magnetism.

When the sizes E and C respectively represent an effort generalized (like a force, a couple, a electric Tension, a Pression, etc) and a generalized coordinate (as the distance, the angular position, the electric Charge, the volume of fluid, etc) within the meaning of the mechanical Lagrangienne, hysteresis is associated with a dissipation of energy. This is also the case in the hysteresis of the magnetic material magnetizing. The interior surface of the hysteresis loop corresponds to energy used to traverse the cycle (and transform in heat). In the electric transformers, the power lost because of the hysteresis of the cores of the transformers is called losses iron.

The phenomena of hysteresis are examples of phenomena irreversible S in Physique.

The concept of hysteresis in social sciences

Derived from its physical definition, the Concept of hysteresis also exists in Social sciences.

Thus, in the theory developed in Sociology by Pierre Bourdieu, the hysteresis of L habitus indicates the phenomenon by which the provisions acquired by socialization of an individual in a definite social space perdurent in time.

In other words, even if the individual in question finds himself in a different social space (change of status, of position social, or evolution of this social space), it will tend to preserve at least partly, or at least during a certain time, the initial provisions.

This hysteresis of the habitus can lead the individual besides (or better known as, its provisions) to a situation of temporary or final maladjustment in the new conditions into force in social space.

Many examples exist in the arts person fields (Don Quichotte), or of daily life (elderly vis-a-vis the use of new technologies, evolution of the relations girl-boys, cases of rise or social regression, etc). Pierre Bourdieu in the Ball of the single people gives another example of the hysteresis of the habitus in the field of the matrimonial strategies of the peasants of Béarn: provisions acquired by the country men in Béarn who were the standard during first half of the 20th century, and who as well touched the manners of relationner with the girls, to speak to them, to consider them, that those having milked more directly with the way of conceiving the marriage, the couple, the love, and of evaluating the social hierarchies according to the criteria specific to the peasants, became obsolete with délittement of the country company in the moitiée second of the 20th century (of which the departure of the girls of the villages towards the cities is an important component). The hysteresis of the habitus of unquestionable peasants, located sometimes well on the country social hierarchy, is this maladjustment of the initial country provisions to the new social space in which they “in spite of them” are located. This maladjustment is an explanatory element of the important celibacy of the aforesaid peasants.

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