First law of thermodynamics

The first law of thermodynamics is a formulation of the law of conservation of energy, adapted for thermodynamic processes. A simple formulation is: "The total energy in a system remains constant, although it may be converted from one form to another." Another common phrasing is that "energy can neither be created nor destroyed". While there are many subtleties and implications that may be more precisely captured in more complex formulations, this is the essential principle of the First Law. It distinguishes in principle two forms of energy transfer: heat, and thermodynamic work, for a system of a constant amount of matter. The law also defines the internal energy of a system, an extensive property for taking account of the balance of energies in the system. The law of conservation of energy states that the total energy of any isolated system, which cannot exchange energy or matter, is constant. Energy can be transformed from one form to another, but can be neither created nor destroyed. The first law for a thermodynamic process is often formulated as where denotes the change in the internal energy of a closed system (for which heat or work through the system boundary are possible, but matter transfer is not possible), denotes the energy supplied to the system as heat, and is the thermodynamic work done by the system on its surroundings. An equivalent statement is that perpetual motion machines of the first kind are impossible; work done by a system on its surroundings requires that the system's internal energy decrease or be consumed, so that the amount of internal energy lost by that work must be resupplied as heat by an external energy source or as work by an external machine acting on the system (so that is recovered) to make the system work continuously. The ideal isolated system, of which the entire universe is an example, is often only used as a model. Many systems in practical applications require the consideration of internal chemical or nuclear reactions, as well as transfers of matter into or out of the system.

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related people (2)

Related units (1)

Related concepts (64)

Related courses (107)

Related lectures (731)

Related MOOCs (7)

In thermodynamics, heat is the thermal energy transferred between systems due to a temperature difference. In colloquial use, heat sometimes refers to thermal energy itself. An example of formal vs. informal usage may be obtained from the right-hand photo, in which the metal bar is "conducting heat" from its hot end to its cold end, but if the metal bar is considered a thermodynamic system, then the energy flowing within the metal bar is called internal energy, not heat.

Perpetual motion is the motion of bodies that continues forever in an unperturbed system. A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. This kind of machine is impossible, as it would violate either the first or second law of thermodynamics, or both. These laws of thermodynamics apply regardless of the size of the system.

PHYS-106(a): General physics : thermodynamics

Le but du cours de Physique générale est de donner à l'étudiant les notions de base nécessaires à la compréhension des phénomènes physiques. L'objectif est atteint lorsque l'étudiant est capable de pr

ME-351: Thermodynamics and energetics II

This course will discuss advanced topics in thermodynamics with a focus on studying gas phases, mixtures, phase transformations and combustion. The application of these principles to various practical

ME-251: Thermodynamics and energetics I

The course introduces the basic concepts of thermodynamics and heat transfer, and thermodynamic properties of matter and their calculation. The students will master the concepts of heat, mass, and mom

Ce cours complète le MOOC « Thermodynamique : fondements » qui vous permettra de mettre en application les concepts fondamentaux de la thermodynamique. Pour atteindre cet objectif, le Professeur J.-P

Ce cours vous apportera une compréhension des concepts fondamentaux de la thermodynamique du point de vue de la physique, de la chimie et de l’ingénierie. Il est scindé un deux MOOCs. Première partie:

Plasma State: Properties and Effects PHYS-325: Introduction to plasma physics

Covers the definition and properties of plasma, including ionization and collective effects.

Applications of the First Law of Thermodynamics PHYS-106(h): General physics : thermodynamics

Explores the rules for calculating different types of ideal gas transformations.

Carnot Cycle: Calculations PHYS-106(a): General physics : thermodynamics

Covers the calculation of work in a perfect gas and the Carnot cycle.