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Sadi Carnot citations

Nicolas Léonard Sadi Carnot, né le 1er juin 1796 à Paris et mort le 24 août 1832 à Ivry-sur-Seine ou à Paris, usuellement appelé Sadi Carnot, est un physicien et ingénieur français.

Durant sa courte carrière , Sadi Carnot ne publia qu’un seul livre : Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissance, en 1824, dans lequel il exprima, à l’âge de 27 ans, ce qui s’avéra être le travail de sa vie et un livre important dans l’histoire de la physique.

Dans cet ouvrage il posa les bases d’une discipline entièrement nouvelle, la thermodynamique. À l’époque d’ailleurs, le terme n’existait pas, c’est William Thomson qui l’inventa au milieu du XIXe siècle. Pourtant c’est bien Sadi Carnot, malgré l’imprécision de certains de ses concepts , qui a découvert cette science aussi fondamentale du point de vue théorique que féconde en applications pratiques.

Sadi Carnot formula l’exposé raisonné du moteur thermique et les principes de base selon lesquels toute centrale énergétique, toute automobile, tout moteur à réaction est aujourd’hui conçu. Plus remarquable, cette genèse se fit alors qu’aucun prédécesseur n’avait encore défini la nature et l’étendue du sujet. En s’appuyant sur des préoccupations purement techniciennes, comme l’amélioration des performances de la machine à vapeur, le cheminement intellectuel de Sadi Carnot est original et annonce des évolutions importantes qui intervinrent à cette époque charnière pour la science moderne. Wikipedia  

✵ 1. juin 1796 – 24. août 1832
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Sadi Carnot: 19   citations 0   J'aime

Sadi Carnot: Citations en anglais

“We shall have [a complete theory] only when the laws of Physics shall be extended enough, generalized enough, to make known beforehand all the effects of heat acting in a determined manner on any body.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“[I]f we should find about us only bodies as hot as our furnaces, how can we condense steam? What should we do with it if once produced?”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“[W]hen a body has experienced any changes, and when after a certain number of transformations it returns to precisely its original state, that is, to that state considered in respect to density, to temperature, to mode of aggregation—let us suppose, I say, that this body is found to contain the same quantity of heat that it contained at first, or else that the quantities of heat absorbed or set free in these different transformations are exactly compensated. This fact has never been called in question. It was first admitted without reflection, and verified afterwards in many cases by experiments with the calorimeter. To deny it would be to overthrow the whole theory of heat to which it serves as a basis. For the rest, we may say in passing, the main principles on which the theory of heat rests require the most careful examination. Many experimental facts appear almost inexplicable in the present state of this theory.”

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Nicolas Léonard Sadi Carnot

Reflections on the Motive Power of Heat (1824)

“Notwithstanding the work of all kinds done by steam-engines… their theory is very little understood, and the attempts to improve them are still directed almost by chance.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“[W]e have just described the re-establishment of equilibrium in the caloric, its passage from a… heated body to a cooler one.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“What happens… in a steam-engine…? The caloric developed in the furnace by the effect of the combustion traverses the walls of the boiler, produces steam, and in some way incorporates itself with it. The latter carrying it away, takes it first into the cylinder, where it performs some function, and from thence into the condenser, where it is liquefied by contact with the cold water… [T]he cold water of the condenser takes possession of the caloric… It is heated by the intervention of the steam as if it had been placed directly over the furnace. The steam is here only a means of transporting the caloric.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“The phenomenon of the production of motion by heat has not been considered from a sufficiently general point of view. We have considered it only in machines… [for which] the phenomenon is… incomplete. It becomes difficult to recognize its principles and study its laws. …[T]he principle of the production of motion by heat… must be considered independently of any mechanism or… particular agent. It is necessary to establish principles applicable not only to steam-engines but to all imaginable heat-engines, whatever the working substance and whatever the method by which it is operated.”

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Nicolas Léonard Sadi Carnot

Reflections on the Motive Power of Heat (1824)

“The maximum of motive power resulting from the employment of steam is also the maximum of motive power realizable by any means whatever.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“The production of motion in steam-engines is always accompanied by… the re-establishing of equilibrium in the caloric; that is, its passage from a body in which the temperature is more or less elevated, to another in which it is lower.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“Savery, Newcomen, Smeaton, the famous Watt, Woolf, Trevithick, and some other English engineers, are the veritable creators of the steam-engine.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“There is almost as great a distance between the first apparatus in which the expansive force of steam was displayed and the existing machine, as between the first raft that man ever made and the modern vessel.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“Steam navigation… tends to unite the nations of the earth as inhahitants of one country. …is not this the same as greatly to shorten distances?”

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Nicolas Léonard Sadi Carnot

Reflections on the Motive Power of Heat (1824)

“Wherever there exists a difference of temperature… it is possible to have also the production of impelling power. …All substances in nature can be employed for this purpose, all are susceptible of changes of volume, of successive contractions and dilatations, through the alternation of heat and cold. All are capable of overcoming in their changes of volume certain resistances… A solid… A liquid… An aeriform fluid… If it is enclosed in an expansible space, such as a cylinder provided with a piston, it will produce movements of great extent. Vapors of all substances capable of passing into a gaseous condition, as of alcohol, of mercury, of sulphur, etc., may fulfil the same office as vapor of water. …Most of these… have been proposed, many even have been tried, although… without remarkable success.”

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Nicolas Léonard Sadi Carnot

Reflections on the Motive Power of Heat (1824)

“Heat can evidently be a cause of motion only by virtue of the changes of volume or of form which it produces in bodies.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“Nature, in providing us with combustibles on all sides, has given us the power to produce, at all times and in all places, heat and the impelling power which is the result of it. To develop this power, to appropriate it to our uses, is the object of heat-engines.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“[T]he production of heat alone is not sufficient to give birth to the impelling power: it is necessary that there should also be cold; without it, the heat would be useless.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“Iron and heat are… the supporters, the bases, of the mechanic arts.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“The production of motive power is then due… not to an actual consumption of caloric, but to its transportation from a warm body to a cold body… to its re-establishment of equilibrium…”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

“To take away to-day from England her steam-engines would be to take away at the same time her coal and iron. It would be to dry up all her sources of wealth, to ruin all on which her prosperity depends, in short, to annihilate that colossal power.”

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Nicolas Léonard Sadi Carnot

p, 125
Reflections on the Motive Power of Heat (1824)

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