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Chapter 20

The First Law of Thermodynamics

Systèmes thermodynamiques
Systèmes thermodynamiques
A thermodynamic system is a set of objects whose thermodynamic properties are of interest. The system is considered to be embedded in its surroundings or ...
Travail effectué lors du changement de volume
Travail effectué lors du changement de volume
In mechanics, work is done on an object when the force acting on it displaces the object. In thermodynamics, work done on a system can be estimated when ...
Chemin entre les états thermodynamiques
Chemin entre les états thermodynamiques
Consider the two thermodynamic processes involving an ideal gas that are represented by paths AC and ABC in Figure 1: In the first process for path A to ...
Chaleur et détente libre
Chaleur et détente libre
The work done by a thermodynamic system depends not only on the initial and final states but also on the intermediate states—that is, on the path. ...
Énergie interne
Énergie interne
The internal energy of a thermodynamic system is the sum of the kinetic and potential energies of all the molecules or entities in the system. The kinetic ...
Première loi de la thermodynamique
Première loi de la thermodynamique
A change in the internal energy of a system depends on the the net heat transfer into the system and the net work done by the system. The first law of ...
Première loi de la thermodynamique : résolution de problèmes
Première loi de la thermodynamique : résolution de problèmes
The first law of thermodynamics states that the change in internal energy of the system is equal to the net heat transfer into the system minus the net ...
Processus cycliques et systèmes isolés
Processus cycliques et systèmes isolés
A thermodynamic system with zero heat exchange and work is an isolated system. For these systems, the internal energy remains constant. In the case of a ...
Procédés isothermes
Procédés isothermes
A thermodynamic process that occurs at constant temperature is called an isothermal process. Heat slowly flows into the system or out of the system to ...
Processus isochores et isobares
Processus isochores et isobares
A thermodynamic process that occurs at constant volume is called an isochoric process. According to the first law of thermodynamics, heat supplied or ...
Capacités thermiques d’un gaz parfait I
Capacités thermiques d’un gaz parfait I
Heat capacity is the ratio of heat absorbed by the substance corresponding to its temperature change. It is also called thermal capacity and the SI unit ...
Capacités thermiques d’un gaz parfait II
Capacités thermiques d’un gaz parfait II
For a system that undergoes a thermodynamic process at a constant volume condition, the heat absorbed is used only to increase the system's internal ...
Capacités thermiques d’un gaz parfait III
Capacités thermiques d’un gaz parfait III
The number of independent ways a gas molecule can move along straight line, rotate, and vibrate is called its degrees of freedom. Supposing d represents ...
Procédés adiabatiques pour un gaz parfait
Procédés adiabatiques pour un gaz parfait
When an ideal gas is compressed adiabatically, that is, without adding heat, work is done on it, and its temperature increases. In an adiabatic expansion, ...
Pression et volume dans un processus adiabatique
Pression et volume dans un processus adiabatique
Free expansion of a gas is an adiabatic process. However, there are few differences between free expansion and adiabatic expansion. During free expansion, ...
Travail effectué dans un processus adiabatique
Travail effectué dans un processus adiabatique
Consider the adiabatic compression of an ideal gas in the cylinder of an automobile diesel engine. The gasoline vapor is injected into the cylinder of an ...
Potentiels thermodynamiques
Potentiels thermodynamiques
Thermodynamic potentials are state functions that are extremely useful in analyzing a thermodynamic system. They have dimensions of energy. The four ...
Relations thermodynamiques de Maxwell
Relations thermodynamiques de Maxwell
Maxwell's thermodynamic relations are very useful in solving problems in thermodynamics. Each of Maxwell's relations relates a partial ...
Effet Joule-Thomson
Effet Joule-Thomson
The Joule-Thomson effect, also known as the Joule-Kelvin effect, describes the temperature change of a fluid when it is forced through a valve or porous ...
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