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Pressure Pressure Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure Gauge pressure (also spelled gage pressure)[a] is the pressure relative to the ambient pressure. Various units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the SI unit SI unit of pressure, the pascal (Pa), for example, is one newton per square metre; similarly, the poundforce per square inch (psi) is the traditional unit of pressure in the imperial and US customary systems. Pressure may also be expressed in terms of standard atmospheric pressure; the atmosphere (atm) is equal to this pressure, and the torr is defined as 1⁄760 of this [...More...]  "Pressure" on: Wikipedia Yahoo 

Joule (unit) The joule (/dʒuːl/); (symbol: J), is a derived unit of energy in the International System of Units.[1] It is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre (1 newton metre or N⋅m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second [...More...]  "Joule (unit)" on: Wikipedia Yahoo 

Carnot Heat Engine A Carnot heat engine[2] is a theoretical engine that operates on the reversible Carnot cycle. The basic model for this engine was developed by Nicolas Léonard Sadi Carnot Nicolas Léonard Sadi Carnot in 1824. The Carnot engine model was graphically expanded upon by Benoît Paul Émile Clapeyron in 1834 and mathematically explored by Rudolf Clausius Rudolf Clausius in 1857 from which the concept of entropy emerged. Every thermodynamic system exists in a particular state. A thermodynamic cycle occurs when a system is taken through a series of different states, and finally returned to its initial state. In the process of going through this cycle, the system may perform work on its surroundings, thereby acting as a heat engine. A heat engine acts by transferring energy from a warm region to a cool region of space and, in the process, converting some of that energy to mechanical work. The cycle may also be reversed [...More...]  "Carnot Heat Engine" on: Wikipedia Yahoo 

Quantum Thermodynamics Quantum thermodynamics is the study of the relations between two independent physical theories: thermodynamics and quantum mechanics. The two independent theories address the physical phenomena of light and matter. In 1905 Einstein Einstein argued that the requirement of consistency between thermodynamics and electromagnetism[1] leads to the conclusion that light is quantized obtaining the relation E = h ν displaystyle E=hnu . This paper is the dawn of quantum theory. In a few decades quantum theory became established with an independent set of rules.[2] Currently quantum thermodynamics addresses the emergence of thermodynamic laws from quantum mechanics. It differs from quantum statistical mechanics in the emphasis on dynamical processes out of equilibrium [...More...]  "Quantum Thermodynamics" on: Wikipedia Yahoo 

SI Base Unit The International System of Units International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the metre for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance. The SI base units form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science and technology. The names and symbols of SI base units are written in lowercase, except the symbols of those named after a person, which are written with an initial capital letter [...More...]  "SI Base Unit" on: Wikipedia Yahoo 

Real Gas Real gases are nonhypothetical gases whose molecules occupy space and have interactions; consequently, they adhere to gas laws. To understand the behaviour of real gases, the following must be taken into account:compressibility effects; variable specific heat capacity; van der Waals forces; nonequilibrium thermodynamic effects; issues with molecular dissociation and elementary reactions with variable compositionFor most applications, such a detailed analysis is unnecessary, and the ideal gas approximation can be used with reasonable accuracy. On the other hand, realgas models have to be used near the condensation point of gases, near critical points, at very high pressures, to explain the Joule–Thomson effect Joule–Thomson effect and in other less usual cases [...More...]  "Real Gas" on: Wikipedia Yahoo 

Metre The metre (British spelling and BIPM spelling[1]) or meter (American spelling) (from the French unit mètre, from the Greek noun μέτρον, "measure") is the base unit of length in some metric systems, including the International System of Units International System of Units (SI). The SI unit symbol is m.[2] The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458 second.[1] The metre was originally defined in 1793 as one tenmillionth of the distance from the equator to the North Pole. In 1799, it was redefined in terms of a prototype metre bar (the actual bar used was changed in 1889). In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton86. In 1983, the current definition was adopted. The imperial inch is defined as 0.0254 metres (2.54 centimetres or 25.4 millimetres). One metre is about 3 3⁄8 inches longer than a yard, i.e [...More...]  "Metre" on: Wikipedia Yahoo 

Second The second is the SI base unit SI base unit of time, commonly understood and historically defined as 1/86,400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each. Another intuitive understanding is that it is about the time between beats of a human heart.[nb 1] Mechanical and electric clocks and watches usually have a face with 60 tickmarks representing seconds and minutes, traversed by a second hand and minute hand. Digital clocks and watches often have a twodigit counter that cycles through seconds [...More...]  "Second" on: Wikipedia Yahoo 

Chemical Thermodynamics Chemical thermodynamics Chemical thermodynamics is the study of the interrelation of heat and work with chemical reactions or with physical changes of state within the confines of the laws of thermodynamics. Chemical thermodynamics involves not only laboratory measurements of various thermodynamic properties, but also the application of mathematical methods to the study of chemical questions and the spontaneity of processes. The structure of chemical thermodynamics is based on the first two laws of thermodynamics. Starting from the first and second laws of thermodynamics, four equations called the "fundamental equations of Gibbs" can be derived. From these four, a multitude of equations, relating the thermodynamic properties of the thermodynamic system can be derived using relatively simple mathematics [...More...]  "Chemical Thermodynamics" on: Wikipedia Yahoo 

Statistical Mechanics Statistical mechanics Statistical mechanics is a branch of theoretical physics that uses probability theory to study the average behaviour of a mechanical system whose exact state is uncertain.[1][2][3][note 1] Statistical mechanics Statistical mechanics is commonly used to explain the thermodynamic behaviour of large systems. This branch of statistical mechanics, which treats and extends classical thermodynamics, is known as statistical thermodynamics or equilibrium statistical mechanics. Microscopic mechanical laws do not contain concepts such as temperature, heat, or entropy; however, statistical mechanics shows how these concepts arise from the natural uncertainty about the state of a system when that system is prepared in practice [...More...]  "Statistical Mechanics" on: Wikipedia Yahoo 

Area Area Area is the quantity that expresses the extent of a twodimensional figure or shape, or planar lamina, in the plane [...More...]  "Area" on: Wikipedia Yahoo 

Kilogram The kilogram or kilogramme (symbol: kg) is the base unit of mass in the International System of Units International System of Units (SI), and is defined as being equal to the mass of the International Prototype of the Kilogram Kilogram (IPK, also known as "Le Grand K" or "Big K"),[2] a cylinder of platinumiridium alloy stored by the International Bureau of Weights and Measures International Bureau of Weights and Measures at SaintCloud, France. The kilogram was originally defined as the mass of a litre (cubic decimetre) of water at its freezing point. That was an inconvenient quantity to precisely replicate, so in the late 18th century a platinum artefact was fashioned as a standard for the kilogram [...More...]  "Kilogram" on: Wikipedia Yahoo 

Thermal Efficiency In thermodynamics, the thermal efficiency ( η t h displaystyle eta _ th , ) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a steam turbine or a steam engine, a boiler, furnace, or a refrigerator for example. For a heat engine, thermal efficiency is the fraction of the energy added by heat (primary energy) that is converted to net work output (secondary energy) [...More...]  "Thermal Efficiency" on: Wikipedia Yahoo 

Second Law Of Thermodynamics The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. The total entropy can remain constant in ideal cases where the system is in a steady state (equilibrium), or is undergoing a reversible process. In all spontaneous processes,[1] the total entropy always increases and the process is irreversible. The increase in entropy accounts for the irreversibility of natural processes[according to whom?], and the asymmetry between future and past. Historically, the second law was an empirical finding that was accepted as an axiom of thermodynamic theory. Statistical thermodynamics, classical or quantum, explains the microscopic origin of the law. The second law has been expressed in many ways [...More...]  "Second Law Of Thermodynamics" on: Wikipedia Yahoo 

Third Law Of Thermodynamics The third law of thermodynamics is sometimes stated as follows, regarding the properties of systems in equilibrium at absolute zero temperature:The entropy of a perfect crystal at absolute zero is exactly equal to zero.At absolute zero (zero kelvin), the system must be in a state with the minimum possible energy, and the above statement of the third law holds true provided that the perfect crystal has only one minimum energy state. Entropy Entropy is related to the number of accessible microstates, and for a system consisting of many particles, quantum mechanics indicates that there is only one unique state (called the ground state) with minimum energy.[1] If the system does not have a welldefined order (if its order is glassy, for example), then in practice there will remain some finite entropy as the system is brought to very low temperatures as the system becomes locked into a configuration with nonminimal energy [...More...]  "Third Law Of Thermodynamics" on: Wikipedia Yahoo 

Zeroth Law Of Thermodynamics The zeroth law of thermodynamics states that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other. Accordingly, thermal equilibrium between systems is a transitive relation. Two systems are said to be in the relation of thermal equilibrium if they are linked by a wall permeable only to heat and they do not change over time.[1] As a convenience of language, systems are sometimes also said to be in a relation of thermal equilibrium if they are not linked so as to be able to transfer heat to each other, but would not do so if they were connected by a wall permeable only to heat. The physical meaning is expressed by Maxwell in the words: "All heat is of the same kind".[2] Another statement of the law is "All diathermal walls are equivalent".[3] The law is important for the mathematical formulation of thermodynamics, which needs the assertion that the relation of thermal equilibrium is an equivalence relation [...More...]  "Zeroth Law Of Thermodynamics" on: Wikipedia Yahoo 