first law of thermodynamics
qânun-e naxost-e garâtavânik
Fr.: première loi de la thermodynamique
The total energy of a → closed system is constant. This means that energy can be changed from one form to another, or transferred from one system to another, but it cannot be created or destroyed. A mathematical formulation of the first law is: δQ = δU + δW, where δQ is the heat transferred to the system, δU the change in internal energy (resulting in a rise or fall of temperature), and δW is the work done by the system.
→ first; → law; → thermodynamics.
local thermodynamic equilibrium (LTE)
tarâzmandi-ye garmâtavânik-e mahali
Fr.: équilibre thermodynamique local
The assumption that all distribution functions characterizing the material and its interaction with the radiation field at a point in the star are given by → thermodynamic equilibrium relations at local values of the temperature and density.
→ local; → thermodynamic; → equilibrium.
non-local thermodynamic equilibrium (NLTE)
tarâzmandi-ye garmâtavânik-e nâmahali
Fr.: hors équilibre thermodynamique local
A physical condition in which the assumption of the → local thermodynamic equilibrium does not hold.
second law of thermodynamics
qânun-e dovom-e garmâtavânik
Fr.: deuxième loi de la thermodynamique
1) Heat cannot be transferred from a colder to a hotter body without some other effect, i.e.
without → work being done. Expressed in terms of
→ entropy: the entropy of an
→ isolated system tends toward a maximum and its
available energy tends toward a minimum.
→ second; → law; → thermodynamics.
Fr.: thermodynamique statistique
Same as → statistical mechanics.
→ statistical; → thermodynamics.
Of or pertaining to → thermodynamics.
Fr.: équilibre thermodynamique
The condition of a → thermodynamic system in which the available → energy is distributed uniformly among all the possible forms of energy. Furthermore, all → thermodynamic process es must be exactly balanced by their reverse processes. For example, inside a star there will be as many → ionizations of helium per second as there are → recombinations of free electrons and helium ions. Se also → local thermodynamic equilibrium (LTE).
→ thermodynamic; → equilibrium.
Fr.: chemin thermodynamique
The loci of various changes between two → states through which a → thermodynamic system passes during a → thermodynamic process.
→ thermodynamic; → path.
Fr.: potentiel thermodynaique
A measure of the energy level of a → thermodynamic system. It represents the amount of → work obtainable when the system undergoes a → change. The main types of thermodynamic potential are: → internal energy, → enthalpy, the → Helmholtz free energy, and the → Gibbs free energy.
→ thermodynamic; → potential.
Fr.: processus thermodynamique
An ordered set of → equilibrium states undergone by a → thermodynamic system. Thermodynamics processes have various types: → cyclic process, → reversible process, and → irreversible process, → isothermal process, → adiabatic process, → isentropic process.
→ thermodynamic; → process.
Fr.: système thermodynamique
A quantity of substance or a working machine which in a well-defined way is set apart from its → environment. The boundary between the system and its surroundings can be real or an imaginary mathematical envelope. A thermodynamic system is not necessarily bound to a predefined geometry. Thermodynamic systems can be divided into three types: → open systems, → closed systems, and → isomated systems.
→ thermodynamic; → system.
Fr.: température thermodynamique
A temperature scale, measured in → kelvin (K), that is related to the energy possessed by matter; it was formerly known as → absolute temperature. The zero point on the scale (0 K) is absolute zero. Thermodynamic temperature can be converted to temperature on the → Celsius scale by subtracting 273.15.
→ thermodynamic; → temperature.
A branch of physics concerned with the relations between heat and other forms of energy and how these affect temperature, pressure, volume, mechanical action, and work.
→ thermo-; → dynamics, coined by the Scottish physicist William Thomson (Lord Kelvin, 1824-1907), in 1849.
third law of thermodynamics
qânun-e sevom-e garmâtavânik
Fr.: troisième loi de la thermodynamique
The → entropy of an idealized state of maximum order is zero at the temperature of → absolute zero. Another version of this law: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.
→ third; → law; → thermodynamics.
zeroth law of thermodynamics
qânun-e sefrom-e garmâtavânik
Fr.: loi zéro de la thermodynamique
Two objects that are in → thermal equilibrium with a third object will be in thermal equilibrium with each other.
→ zero; → law; → thermodynamics.