codzienność: Second law of thermodynamics

Evidence: 100 • authority: 72

The second law of thermodynamics is a physical law based on universal empirical observation concerning heat and energy interconversions. A simple statement of the law is that heat always flows spontaneously from hotter to colder regions of matter (or 'downhill' in terms of the temperature gradient). Another statement is: "Not all heat can be converted into work in a cyclic process." These are informal definitions, however; more formal definitions appear below. The second law of thermodynamics establishes the concept of entropy as a physical property of a thermodynamic system. It predicts whether processes are forbidden despite obeying the requirement of conservation of energy as expressed i…

Evidence: 73 • authority: 72

The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. For a thermodynamic process affecting a thermodynamic system without transfer of matter, the law distinguishes two principal forms of energy transfer, heat and thermodynamic work. The law also defines the internal energy of a system, an extensive property for taking account of the balance of heat transfer, thermodynamic work, and matter transfer, into and out of the system. Energy cannot be created or destroyed, but it can be transformed from one form to another. In an externally isolated system, with internal changes, the sum of all forms of energy is constant. A…

Evidence: 65 • authority: 72

In thermodynamics, heat is defined as energy in transfer between a body and its surroundings, other than through thermodynamic work or through transfer of matter. Rather than by mechanical or other effects in the surroundings, thermodynamic work is defined through changes in the system's macroscopic state variables, in conjugate pairs such as pressure and volume, or magnetisation and magnetic field strength. The thermodynamic definition of heat is by exclusion of other defined modes of transfer in order to ensure a strict logical distinction. In the process of transfer, heat is not necessarily conserved, but can be generated (though not destroyed) by friction. In thermodynamics, temperature…

Evidence: 53 • authority: 72

A Carnot heat engine (English: kar-NOH, French: [kaʁno]) is a theoretical heat engine that operates on the Carnot cycle. The basic model for this engine was developed by French military engineer Nicolas Léonard Sadi Carnot in 1824. The Carnot engine model was graphically expanded by Benoît Paul Émile Clapeyron in 1834 and mathematically explored by Rudolf Clausius in 1857, work that led to the fundamental thermodynamic concept of entropy. The Carnot engine is the most efficient heat engine which is theoretically possible. The efficiency depends only upon the absolute temperatures of the hot and cold heat reservoirs between which it operates. A heat engine acts by transferring energy from a…

Evidence: — • authority: 72

The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium. The laws also use various parameters for thermodynamic processes, such as thermodynamic work and heat, and establish relationships between them. They state empirical facts that form a basis of precluding the possibility of certain phenomena, such as perpetual motion. In addition to their use in thermodynamics, they are important fundamental laws of physics in general and are applicable in other natural sciences. Traditionally, thermodynamics has recognized three fundamental laws, s…

Evidence: — • authority: 72

A heat engine is a system that transfers thermal energy to do mechanical or electrical work. While originally conceived in the context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, particularly electrical, since at least the late 19th century. The heat engine does this by bringing a working substance from a higher state temperature to a lower state temperature. A heat source supplies thermal energy that brings the working substance to the higher temperature state. The working substance does work in the working body of the engine while transferring heat to the colder sink until it reaches a lower temperature state. During this process…

Evidence: — • authority: 72

A Stirling engine is a heat engine that is operated by the cyclic expansion and contraction of air or other gas (the working fluid) by exposing it to different temperatures, resulting in a net conversion of heat energy to mechanical work. More specifically, the Stirling engine is a closed-cycle regenerative heat engine, with a permanent gaseous working fluid. Closed-cycle, in this context, means a thermodynamic system in which the working fluid is permanently contained within the system. Regenerative describes the use of a specific type of internal heat exchanger and thermal store, known as the regenerator. Strictly speaking, the inclusion of the regenerator is what differentiates a Stirlin…