نوشته شده در موضوع تولید انرژی رایگان در 24 نوامبر 2016

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In physics, energy is a skill of objects that can be eliminated to other objects or converted into opposite forms.[1] The “ability of a complement to perform work” is a common description, though it is dubious given appetite is not indispensably accessible to do work.[2] For instance, in SI units, appetite is totalled in joules, and one joule is tangible “mechanically”, being a appetite eliminated to an intent by a automatic work of relocating it a stretch of 1 metre opposite a force of 1 newton.[note 1] However, there are many other definitions of energy, depending on a context, such as thermal energy, eager energy, electromagnetic, nuclear, etc., where definitions are successive that are a many convenient.

Common appetite forms embody a kinetic appetite of a relocating object, a intensity appetite stored by an object’s position in a force margin (gravitational, electric or magnetic), a effervescent appetite stored by stretching plain objects, a chemical appetite expelled when a fuel burns, a eager appetite carried by light, and a thermal appetite due to an object’s temperature. All of a many forms of appetite are automobile to other kinds of energy. In Newtonian physics, there is a judgment law of charge of appetite that says that appetite can be conjunction combined nor be destroyed; however, it can change from one form to another.

For “closed systems” with no outmost source or penetrate of energy, a initial law of thermodynamics states that a system’s appetite is consistent unless appetite is eliminated in or out by automatic work or heat, and that no appetite is mislaid in transfer. This means that it is unfit to emanate or destroy energy. While feverishness can always be wholly converted into work in a reversible isothermal enlargement of an ideal gas, for intermittent processes of unsentimental seductiveness in feverishness engines a second law of thermodynamics states that a complement doing work always loses some appetite as rubbish heat. This creates a extent to a volume of feverishness appetite that can do work in a intermittent process, a extent called a accessible energy. Mechanical and other forms of appetite can be remade in a other instruction into thermal appetite though such limitations.[3] The sum appetite of a complement can be distributed by adding adult all forms of appetite in a system.

Examples of appetite mutation embody generating electric appetite from feverishness appetite around a steam turbine, or lifting an intent opposite sobriety regulating electrical appetite pushing a derrick motor. Lifting opposite sobriety performs automatic work on a intent and stores gravitational intensity appetite in a object. If a intent falls to a ground, sobriety does automatic work on a intent that transforms a intensity appetite in a gravitational margin to a kinetic appetite expelled as feverishness on impact with a ground. Our Sun transforms chief intensity appetite to other forms of energy; a sum mass does not diminution due to that in itself (since it still contains a same sum appetite even if in opposite forms), though a mass does diminution when a appetite escapes out to a surroundings, mostly as eager energy.

Mass and appetite are closely related. According to a speculation of mass–energy equivalence, any intent that has mass when still in a support of anxiety (called rest mass) also has an comparable volume of appetite whose form is called rest appetite in that frame, and any additional appetite acquired by a intent above that rest appetite will boost an object’s mass. For example, with a supportive adequate scale, one could bulk an boost in mass after heating an object.

Living organisms need accessible appetite to stay alive, such as a appetite humans get from food. Civilisation gets a appetite it needs from appetite resources such as hoary fuels, chief fuel, or renewable energy. The processes of Earth’s meridian and ecosystem are driven by a eager appetite Earth receives from a intent and a geothermal appetite contained within a earth.
In biology, appetite can be suspicion of as what’s indispensable to keep entropy low.


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The sum appetite of a complement can be subdivided and personal in several ways. For example, exemplary mechanics distinguishes between kinetic energy, that is dynamic by an object’s mutation by space, and intensity energy, that is a duty of a position of an intent within a field. It might also be accessible to heed gravitational energy, thermal energy, several forms of chief appetite (which implement potentials from a chief force and a diseased force), electric appetite (from a electric field), and captivating appetite (from a captivating field), among others. Many of these classifications overlap; for instance, thermal appetite customarily consists partly of kinetic and partly of intensity energy.

Some forms of appetite are a varying brew of both intensity and kinetic energy. An instance is automatic appetite that is a sum of (usually macroscopic) kinetic and intensity appetite in a system. Elastic appetite in materials is also contingent on electrical intensity appetite (among atoms and molecules), as is chemical energy, that is stored and expelled from a fountainhead of electrical intensity appetite between electrons, and a molecules or atomic nuclei that attract them.[need selection to verify].The list is also not indispensably complete. Whenever earthy scientists learn that a certain materialisation appears to violate a law of appetite conservation, new forms are typically combined that comment for a discrepancy.

Heat and work are special cases in that they are not properties of systems, though are instead properties of processes that send energy. In ubiquitous we can't bulk how many feverishness or work are benefaction in an object, though rather customarily how many appetite is eliminated among objects in certain ways during a occurrence of a given process. Heat and work are totalled as certain or disastrous depending on that side of a send we perspective them from.

Potential energies are mostly totalled as certain or disastrous depending on possibly they are incomparable or reduction than a appetite of a specified bottom state or pattern such as dual interacting bodies being perpetually distant apart. Wave energies (such as eager or sound energy), kinetic energy, and rest appetite are any incomparable than or equal to 0 given they are totalled in comparison to a bottom state of 0 energy: “no wave”, “no motion”, and “no inertia”, respectively.

The distinctions between opposite kinds of appetite is not always clear-cut. As Richard Feynman points out:

These notions of intensity and kinetic appetite count on a thought of length scale. For example, one can pronounce of macroscopic intensity and kinetic energy, that do not embody thermal intensity and kinetic energy. Also what is called chemical intensity appetite is a perceivable notion, and closer hearing shows that it is unequivocally a sum of a intensity and kinetic appetite on a atomic and subatomic scale. Similar remarks request to chief “potential” appetite and many other forms of energy. This coherence on length scale is non-problematic if a several length beam are decoupled, as is mostly a box … though difficulty can arise when opposite length beam are coupled, for instance when attrition translates perceivable work into little thermal energy.

Some examples of opposite kinds of energy:


The word energy derives from a Ancient Greek: ἐνέργεια energeia “activity, operation”,[4] that presumably appears for a initial time in a work of Aristotle in a 4th century BC. In contrariety to a complicated definition, energeia was a qualitative philosophical concept, extended adequate to embody ideas such as complacency and pleasure.

In a late 17th century, Gottfried Leibniz due a thought of a Latin: vis viva, or critical force, that tangible as a product of a mass of an intent and a quickness squared; he believed that sum vis viva was conserved. To comment for negligence due to friction, Leibniz theorized that thermal appetite consisted of a pointless suit of a simple tools of matter, a perspective common by Isaac Newton, nonetheless it would be some-more than a century until this was generally accepted. The complicated analog of this property, kinetic energy, differs from vis viva customarily by a cause of two.

In 1807, Thomas Young was presumably a initial to use a tenure “energy” instead of vis viva, in a complicated sense.[5]Gustave-Gaspard Coriolis described “kinetic energy” in 1829 in a complicated sense, and in 1853, William Rankine coined a tenure “potential energy”. The law of charge of appetite was also initial presumed in a early 19th century, and relates to any removed system. It was argued for some years possibly feverishness was a earthy substance, dubbed a caloric, or merely a earthy quantity, such as momentum. In 1845 James Prescott Joule detected a couple between automatic work and a era of heat.

These developments led to a speculation of charge of energy, formalized mostly by William Thomson (Lord Kelvin) as a margin of thermodynamics. Thermodynamics aided a fast enlargement of explanations of chemical processes by Rudolf Clausius, Josiah Willard Gibbs, and Walther Nernst. It also led to a mathematical plan of a judgment of entropy by Clausius and to a introduction of laws of eager appetite by Jožef Stefan. According to Noether’s theorem, a charge of appetite is a effect of a fact that a laws of production do not change over time.[6] Thus, given 1918, theorists have accepted that a law of charge of appetite is a approach mathematical effect of a translational balance of a apportion conjugate to energy, namely time.

Units of measure

In 1843 James Prescott Joule exclusively detected a automatic comparable in a array of experiments. The many famous of them used a “Joule apparatus”: a forward weight, trustworthy to a string, caused revolution of a paddle enthralled in water, many insulated from feverishness transfer. It showed that a gravitational intensity appetite mislaid by a weight in forward was equal to a inner appetite gained by a H2O by attrition with a paddle.

In a International System of Units (SI), a section of appetite is a joule, named after James Prescott Joule. It is a successive unit. It is equal to a appetite spent (or work done) in requesting a force of one newton by a stretch of one metre. However appetite is also voiced in many other units not partial of a SI, such as ergs, calories, British Thermal Units, kilowatt-hours and kilocalories, that need a acclimatisation cause when voiced in SI units.

The SI section of appetite rate (energy per section time) is a watt, that is a joule per second. Thus, one joule is one watt-second, and 3600 joules equal one watt-hour. The CGS appetite section is a erg and a majestic and US prevalent section is a feet pound. Other appetite units such as a electronvolt, food calorie or thermodynamic kcal (based on a feverishness change of H2O in a heating process), and BTU are used in specific areas of scholarship and commerce.

Scientific use

Classical mechanics

Classical mechanics
F→=ma→{displaystyle {vec {F}}=m{vec {a}}}

In exemplary mechanics, appetite is a conceptually and mathematically useful property, as it is a withheld quantity. Several formulations of mechanics have been grown regulating appetite as a core concept.

Work, a form of energy, is force times distance.

W=∫CF⋅ds{displaystyle W=int _{C}mathbf {F} cdot mathrm {d} mathbf {s} }

This says that a work (W{displaystyle W}) is equal to a line integral of a force F along a trail C; for sum see a automatic work article. Work and so appetite is support dependent. For example, cruise a round being strike by a bat. In a center-of-mass anxiety frame, a bat does no work on a ball. But, in a anxiety support of a chairman overhanging a bat, substantial work is finished on a ball.

The sum appetite of a complement is infrequently called a Hamiltonian, after William Rowan Hamilton. The exemplary equations of suit can be combined in terms of a Hamiltonian, even for rarely formidable or epitome systems. These exemplary equations have remarkably approach analogs in nonrelativistic quantum mechanics.[7]

Another energy-related judgment is called a Lagrangian, after Joseph-Louis Lagrange. This formalism is as elemental as a Hamiltonian, and both can be used to get a equations of suit or be successive from them. It was invented in a context of exemplary mechanics, though is generally useful in complicated physics. The Lagrangian is tangible as a kinetic appetite minus a intensity energy. Usually, a Lagrange formalism is mathematically some-more accessible than a Hamiltonian for non-conservative systems (such as systems with friction).

Noether’s postulate (1918) states that any differentiable balance of a mutation of a earthy complement has a analogous charge law. Noether’s postulate has turn a elemental apparatus of complicated fanciful production and a calculus of variations. A generalisation of a seminal formulations on constants of suit in Lagrangian and Hamiltonian mechanics (1788 and 1833, respectively), it does not request to systems that can't be modeled with a Lagrangian; for example, dissipative systems with continual symmetries need not have a analogous charge law.


In a context of chemistry, appetite is an charge of a piece as a effect of a atomic, molecular or sum structure. Since a chemical mutation is accompanied by a change in one or some-more of these kinds of structure, it is constantly accompanied by an boost or diminution of appetite of a substances involved. Some appetite is eliminated between a vicinity and a reactants of a greeting in a form of feverishness or light; so a products of a greeting might have some-more or reduction appetite than a reactants. A greeting is pronounced to be exergonic if a final state is reduce on a appetite scale than a initial state; in a box of endergonic reactions a conditions is a reverse. Chemical reactions are constantly not probable unless a reactants overcome an appetite separator famous as a activation energy. The speed of a chemical greeting (at given temperature T) is compared to a activation energy E, by a Boltzmann’s race factor eE/kT – that is a luck of proton to have appetite incomparable than or equal to E during a given temperature T. This exponential coherence of a greeting rate on feverishness is famous as a Arrhenius equation.The activation appetite required for a chemical greeting can be in a form of thermal energy.


In biology, appetite is an charge of all biological systems from a stratosphere to a smallest critical organism. Within an mammal it is obliged for enlargement and enlargement of a biological dungeon or an organelle of a biological organism. Energy is so mostly pronounced to be stored by cells in a structures of molecules of substances such as carbohydrates (including sugars), lipids, and proteins, that recover appetite when reacted with oxygen in respiration. In tellurian terms, a tellurian comparable (H-e) (Human appetite conversion) indicates, for a given volume of appetite expenditure, a relations apportion of appetite indispensable for tellurian metabolism, presumption an normal tellurian appetite outlay of 12,500 kJ per day and a elemental metabolic rate of 80 watts. For example, if a bodies run (on average) during 80 watts, afterwards a light tuber regulating during 100 watts is regulating during 1.25 tellurian equivalents (100 ÷ 80) i.e. 1.25 H-e. For a formidable charge of customarily a few seconds’ duration, a chairman can put out thousands of watts, many times a 746 watts in one central horsepower. For tasks durability a few minutes, a fit tellurian can beget maybe 1,000 watts. For an activity that contingency be postulated for an hour, outlay drops to around 300; for an activity kept adult all day, 150 watts is about a maximum.[8] The tellurian comparable assists bargain of appetite flows in earthy and biological systems by expressing appetite units in tellurian terms: it provides a “feel” for a use of a given volume of energy.[9]

Sunlight is also prisoner by plants as chemical intensity energy in photosynthesis, when CO dioxide and H2O (two low-energy compounds) are converted into a high-energy compounds carbohydrates, lipids, and proteins. Plants also recover oxygen during photosynthesis, that is employed by critical organisms as an nucleus acceptor, to recover a appetite of carbohydrates, lipids, and proteins. Release of a appetite stored during photosynthesis as feverishness or light might be triggered astonishing by a spark, in a timberland fire, or it might be finished accessible some-more solemnly for animal or tellurian metabolism, when these molecules are ingested, and catabolism is triggered by enzyme action.

Any critical mammal relies on an outmost source of energy—radiation from a Sun in a box of immature plants, chemical appetite in some form in a box of animals—to be means to grow and reproduce. The daily 1500–2000 Calories (6–8 MJ) endorsed for a tellurian adult are taken as a multiple of oxygen and food molecules, a latter mostly carbohydrates and fats, of that glucose (C6H12O6) and stearin (C57H110O6) are accessible examples. The food molecules are oxidised to CO dioxide and H2O in a mitochondria

C6H12O6 + 6O2 → 6CO2 + 6H2O
C57H110O6 + 81.5O2 → 57CO2 + 55H2O

and some of a appetite is used to modify ADP into ATP.

ADP + HPO42− → ATP + H2O

The rest of a chemical appetite in O2[10] and a carbohydrate or fat is converted into heat: a ATP is used as a arrange of “energy currency”, and some of a chemical appetite it contains is used for other metabolism when ATP reacts with OH groups and eventually splits into ADP and phosphate (at any theatre of a metabolic pathway, some chemical appetite is converted into heat). Only a little fragment of a bizarre chemical appetite is used for work:[note 2]

gain in kinetic appetite of a competitor during a 100 m race: 4 kJ
gain in gravitational intensity appetite of a 150 kg weight carried by 2 metres: 3 kJ
Daily food intake of a normal adult: 6–8 MJ

It would seem that critical organisms are remarkably emasculate (in a earthy sense) in their use of a appetite they accept (chemical appetite or radiation), and it is loyal that many genuine machines conduct aloft efficiencies. In flourishing organisms a appetite that is converted to feverishness serves a critical purpose, as it allows a mammal hankie to be rarely systematic with courtesy to a molecules it is built from. The second law of thermodynamics states that appetite (and matter) tends to turn some-more uniformly widespread out opposite a universe: to combine appetite (or matter) in one specific place, it is required to widespread out a incomparable volume of appetite (as heat) opposite a residue of a star (“the surroundings”).[note 3] Simpler organisms can grasp aloft appetite efficiencies than some-more formidable ones, though a formidable organisms can occupy ecological niches that are not accessible to their easier brethren. The acclimatisation of a apportionment of a chemical appetite to feverishness during any step in a metabolic pathway is a earthy reason behind a pyramid of biomass celebrated in ecology: to take usually a initial step in a food chain, of a estimated 124.7 Pg/a of CO that is firm by photosynthesis, 64.3 Pg/a (52%) are used for a metabolism of immature plants,[11] i.e. reconverted into CO dioxide and heat.

Earth sciences

In geology, continental drift, towering ranges, volcanoes, and earthquakes are phenomena that can be explained in terms of appetite transformations in a Earth’s interior,[12] while meteorological phenomena like wind, rain, hail, snow, lightning, tornadoes and hurricanes are all a outcome of appetite transformations brought about by solar appetite on a atmosphere of a world Earth.

Sunlight might be stored as gravitational intensity appetite after it strikes a Earth, as (for example) H2O evaporates from oceans and is deposited on plateau (where, after being expelled during a hydroelectric dam, it can be used to expostulate turbines or generators to furnish electricity). Sunlight also drives many continue phenomena, save those generated by volcanic events. An instance of a solar-mediated continue eventuality is a hurricane, that occurs when vast inconstant areas of comfortable ocean, exhilarated over months, give adult some of their thermal appetite astonishing to appetite a few days of aroused atmosphere movement.

In a slower process, hot spoil of atoms in a core of a Earth releases heat. This thermal appetite drives image tectonics and might lift mountains, around orogenesis. This delayed lifting represents a kind of gravitational intensity appetite storage of a thermal energy, that might be after expelled to active kinetic appetite in landslides, after a triggering event. Earthquakes also recover stored effervescent intensity appetite in rocks, a store that has been constructed eventually from a same hot feverishness sources. Thus, according to benefaction understanding, informed events such as landslides and earthquakes recover appetite that has been stored as intensity appetite in a Earth’s gravitational margin or effervescent aria (mechanical intensity energy) in rocks. Prior to this, they paint recover of appetite that has been stored in complicated atoms given a fall of long-destroyed supernova stars combined these atoms.


In cosmology and astronomy a phenomena of stars, nova, supernova, quasars and gamma-ray bursts are a universe’s highest-output appetite transformations of matter. All stellar phenomena (including solar activity) are driven by several kinds of appetite transformations. Energy in such transformations is possibly from gravitational fall of matter (usually molecular hydrogen) into several classes of astronomical objects (stars, black holes, etc.), or from chief alloy (of lighter elements, essentially hydrogen). The chief alloy of hydrogen in a Sun also releases another store of intensity appetite that was combined during a time of a Big Bang. At that time, according to theory, space stretched and a star cooled too fast for hydrogen to totally compound into heavier elements. This meant that hydrogen represents a store of intensity appetite that can be expelled by fusion. Such a alloy routine is triggered by feverishness and vigour generated from gravitational fall of hydrogen clouds when they furnish stars, and some of a alloy appetite is afterwards remade into sunlight.

Quantum mechanics

In quantum mechanics, appetite is tangible in terms of a appetite user as a time derivative of a call function. The Schrödinger equation equates a appetite user to a full appetite of a molecule or a system. Its regulation can be deliberate as a clarification of dimensions of appetite in quantum mechanics. The Schrödinger equation describes a space- and time-dependence of a solemnly changing (non-relativistic) call duty of quantum systems. The resolution of this equation for a firm complement is dissimilar (a set of accessible states, any characterized by an appetite level) that regulation in a judgment of quanta. In a resolution of a Schrödinger equation for any oscillator (vibrator) and for electromagnetic waves in a vacuum, a ensuing appetite states are compared to a bulk by Planck’s relation: E=hν{displaystyle E=hnu } (where h{displaystyle h} is Planck’s constant and ν{displaystyle nu } a frequency). In a box of an electromagnetic call these appetite states are called quanta of light or photons.


When calculating kinetic appetite (work to accelerate a mass from 0 speed to some calculable speed) relativistically – regulating Lorentz transformations instead of Newtonian mechanics – Einstein detected an astonishing by-product of these calculations to be an appetite tenure that does not disappear during 0 speed. He called it rest mass energy: appetite that any mass contingency possess even when being during rest. The volume of appetite is directly proportional to a mass of body:

E=mc2{displaystyle E=mc^{2}},


m is a mass,
c is a speed of light in vacuum,
E is a rest mass energy.

For example, cruise electron–positron annihilation, in that a rest mass of particular particles is destroyed, though a sluggishness comparable of a complement of a dual particles (its immutable mass) stays (since all appetite is compared with mass), and this sluggishness and immutable mass is carried off by photons that away are massless, though as a complement keep their mass. This is a reversible routine – a opposite routine is called span origination – in that a rest mass of particles is combined from appetite of dual (or more) annihilating photons. In this complement a matter (electrons and positrons) is broken and altered to non-matter appetite (the photons). However, a sum complement mass and appetite do not change during this interaction.

In ubiquitous relativity, a stress–energy tensor serves as a source tenure for a gravitational field, in severe analogy to a approach mass serves as a source tenure in a non-relativistic Newtonian approximation.[13]

It is not odd to hear that appetite is “equivalent” to mass. It would be some-more accurate to state that any appetite has an sluggishness and sobriety equivalent, and given mass is a form of energy, afterwards mass too has sluggishness and sobriety compared with it.

In exemplary physics, appetite is a scalar quantity, a authorized conjugate to time. In special relativity appetite is also a scalar (although not a Lorentz scalar though a time member of a energy–momentum 4-vector).[13] In other words, appetite is immutable with honour to rotations of space, though not immutable with honour to rotations of space-time (= boosts).


Energy might be remade between opposite forms during several efficiencies. Items that renovate between these forms are called transducers. Examples of transducers embody a battery, from chemical appetite to electric energy; a dam: gravitational intensity appetite to kinetic appetite of relocating H2O (and a blades of a turbine) and eventually to electric appetite by an electric generator; or a feverishness engine, from feverishness to work.

There are despotic boundary to how good feverishness can be converted into work in a intermittent process, e.g. in a feverishness engine, as described by Carnot’s postulate and a second law of thermodynamics. However, some appetite transformations can be utterly efficient. The instruction of transformations in appetite (what kind of appetite is remade to what other kind) is mostly dynamic by entropy (equal appetite widespread among all accessible degrees of freedom) considerations. In use all appetite transformations are accessible on a tiny scale, though certain incomparable transformations are not accessible given it is statistically doubtful that appetite or matter will incidentally pierce into some-more strong forms or smaller spaces.

Energy transformations in a star over time are characterized by several kinds of intensity appetite that has been accessible given a Big Bang after being “released” (transformed to some-more active forms of appetite such as kinetic or eager energy) when a triggering resource is available. Familiar examples of such processes embody chief decay, in that appetite is expelled that was creatively “stored” in complicated isotopes (such as uranium and thorium), by nucleosynthesis, a routine eventually regulating a gravitational intensity appetite expelled from a gravitational fall of supernovae, to store appetite in a origination of these complicated elements before they were incorporated into a solar complement and a Earth. This appetite is triggered and expelled in chief production bombs or in polite chief appetite generation. Similarly, in a box of a chemical explosion, chemical intensity appetite is remade to kinetic appetite and thermal appetite in a unequivocally brief time. Yet another instance is that of a pendulum. At a top points a kinetic appetite is 0 and a gravitational intensity appetite is during maximum. At a lowest indicate a kinetic appetite is during extent and is equal to a diminution of intensity energy. If one (unrealistically) assumes that there is no attrition or other losses, a acclimatisation of appetite between these processes would be perfect, and a pendulum would continue overhanging forever.

Energy is also eliminated from intensity appetite (Ep{displaystyle E_{p}}) to kinetic appetite (Ek{displaystyle E_{k}}) and afterwards behind to intensity appetite constantly. This is referred to as charge of energy. In this sealed system, appetite can't be combined or destroyed; therefore, a initial appetite and a final appetite will be equal to any other. This can be demonstrated by a following:

Epi+Eki=EpF+EkF{displaystyle E_{pi}+E_{ki}=E_{pF}+E_{kF}}


The equation can afterwards be simplified serve given Ep=mgh{displaystyle E_{p}=mgh} (mass times acceleration due to sobriety times a height) and Ek=12mv2{displaystyle E_{k}={frac {1}{2}}mv^{2}} (half mass times quickness squared). Then a sum volume of appetite can be found by adding Ep+Ek=Etotal{displaystyle E_{p}+E_{k}=E_{total}}.

Conservation of appetite and mass in transformation

Energy gives arise to weight when it is trapped in a complement with 0 momentum, where it can be weighed. It is also comparable to mass, and this mass is always compared with it. Mass is also comparable to a certain volume of energy, and serve always appears compared with it, as described in mass-energy equivalence. The regulation E = mc², successive by Albert Einstein (1905) quantifies a attribute between rest-mass and rest-energy within a judgment of special relativity. In opposite fanciful frameworks, identical formulas were successive by J. J. Thomson (1881), Henri Poincaré (1900), Friedrich Hasenöhrl (1904) and others (see Mass-energy equivalence#History for serve information).

Matter might be converted to appetite (and clamp versa), though mass can't ever be destroyed; rather, mass/energy equilibrium stays a consistent for both a matter and a energy, during any routine when they are converted into any other. However, given c2{displaystyle c^{2}} is intensely vast relations to typical tellurian scales, a acclimatisation of typical volume of matter (for example, 1 kg) to other forms of appetite (such as heat, light, and other radiation) can acquit extensive amounts of appetite (~1016{displaystyle 9times 10^{16}} joules = 21 megatons of TNT), as can be seen in chief reactors and chief weapons. Conversely, a mass comparable of a section of appetite is minuscule, that is given a detriment of appetite (loss of mass) from many systems is formidable to bulk by weight, unless a appetite detriment is unequivocally large. Examples of appetite mutation into matter (i.e., kinetic appetite into particles with rest mass) are found in high-energy nuclear physics.

Reversible and non-reversible transformations

Thermodynamics divides appetite mutation into dual kinds: reversible processes and irrevocable processes. An irrevocable routine is one in that appetite is dissolute (spread) into dull appetite states accessible in a volume, from that it can't be recovered into some-more strong forms (fewer quantum states), though plunge of even some-more energy. A reversible routine is one in that this arrange of abolition does not happen. For example, acclimatisation of appetite from one form of intensity margin to another, is reversible, as in a pendulum complement described above. In processes where feverishness is generated, quantum states of reduce energy, benefaction as probable excitations in fields between atoms, act as a fountainhead for partial of a energy, from that it can't be recovered, in sequence to be converted with 100% potency into other forms of energy. In this case, a appetite contingency partly stay as heat, and can't be totally recovered as serviceable energy, only during a cost of an boost in some other kind of heat-like boost in commotion in quantum states, in a star (such as an enlargement of matter, or a randomisation in a crystal).

As a star evolves in time, some-more and some-more of a appetite becomes trapped in irrevocable states (i.e., as feverishness or other kinds of increases in disorder). This has been referred to as a unavoidable thermodynamic feverishness genocide of a universe. In this feverishness genocide a appetite of a star does not change, though a fragment of appetite that is accessible to do work by a feverishness engine, or be remade to other serviceable forms of appetite (through a use of generators trustworthy to feverishness engines), grows reduction and less.

Conservation of energy

According to charge of energy, appetite can conjunction be combined (produced) nor broken by itself. It can customarily be transformed. The sum influx of appetite into a complement contingency equal a sum outflow of appetite from a system, and a change in a appetite contained within a system. Energy is theme to a despotic tellurian charge law; that is, whenever one measures (or calculates) a sum appetite of a complement of particles whose interactions do not count categorically on time, it is found that a sum appetite of a complement always stays constant.[14]

Richard Feynman pronounced during a 1961 lecture:[15]

There is a fact, or if we wish, a law, ruling all healthy phenomena that are famous to date. There is no famous difference to this law—it is accurate so distant as we know. The law is called a conservation of energy. It states that there is a certain quantity, that we call energy, that does not change in plural changes that inlet undergoes. That is a many epitome idea, given it is a mathematical principle; it says that there is a numerical apportion that does not change when something happens. It is not a outline of a mechanism, or anything concrete; it is usually a bizarre fact that we can calculate some series and when we finish examination inlet go by her tricks and calculate a series again, it is a same.

Most kinds of appetite (with gravitational appetite being a critical exception)[16] are theme to despotic inner charge laws as well. In this case, appetite can customarily be exchanged between adjacent regions of space, and all observers establish as to a volumetric firmness of appetite in any given space. There is also a tellurian law of charge of energy, saying that a sum appetite of a star can't change; this is a inference of a inner law, though not clamp versa.[3][15]

This law is a elemental element of physics. As shown rigorously by Noether’s theorem, a charge of appetite is a mathematical effect of translational balance of time,[17] a skill of many phenomena next a vast scale that creates them eccentric of their locations on a time coordinate. Put differently, yesterday, today, and tomorrow are physically indistinguishable. This is given appetite is a apportion that is authorized conjugate to time. This mathematical enigma of appetite and time also regulation in a doubt element – it is unfit to conclude a accurate volume of appetite during any clear time interval. The doubt element should not be confused with appetite charge – rather it provides mathematical boundary to that appetite can in element be tangible and measured.

Each of a simple army of inlet is compared with a opposite form of intensity energy, and all forms of intensity appetite (like all other forms of energy) appears as complement mass, whenever present. For example, a dense open will be somewhat some-more vast than before it was compressed. Likewise, whenever appetite is eliminated between systems by any mechanism, an compared mass is eliminated with it.

In quantum mechanics appetite is voiced regulating a Hamiltonian operator. On any time scales, a doubt in a appetite is by

Δt≥2{displaystyle Delta EDelta tgeq {frac {hbar }{2}}}

which is identical in form to a Heisenberg Uncertainty Principle (but not unequivocally mathematically comparable thereto, given H and t are not boldly conjugate variables, conjunction in exemplary nor in quantum mechanics).

In molecule physics, this inequality permits a qualitative bargain of practical particles that lift momentum, sell by that and with genuine particles, is obliged for a origination of all famous elemental army (more accurately famous as elemental interactions). Virtual photons (which are simply lowest quantum automatic appetite state of photons) are also obliged for electrostatic communication between electric charges (which regulation in Coulomb law), for extemporaneous radiative spoil of exited atomic and chief states, for a Casimir force, for outpost der Waals bond army and some other understandable phenomena.

Energy transfer

Closed systems

Energy send can be deliberate for a special box of systems that are sealed to transfers of matter. The apportionment of a appetite that is eliminated by regressive army over a stretch is totalled as a work a source complement does on a receiving system. The apportionment of a appetite that does not do work during a send is called heat.[note 4] Energy can be eliminated between systems in a accumulation of ways. Examples embody a delivery of electromagnetic appetite around photons, earthy collisions that send kinetic energy,[note 5] and a conductive send of thermal energy.

Energy is particularly withheld and is also locally withheld wherever it can be defined. In thermodynamics, for sealed systems, a routine of appetite send is described by a initial law:[note 6]

ΔE=W+Q{displaystyle Delta {}E=W+Q}


where E{displaystyle E} is a volume of appetite transferred, W{displaystyle W}  represents a work finished on a system, and Q{displaystyle Q} represents a feverishness upsurge into a system. As a simplification, a feverishness term, Q{displaystyle Q}, is infrequently ignored, generally when a thermal efficiency of a send is high.

ΔE=W{displaystyle Delta {}E=W}


This simplified equation is a one used to conclude a joule, for example.

Open systems

Beyond a constraints of sealed systems, open systems can benefit or remove appetite in organisation with matter send (both of these routine are illustrated by fueling an auto, a complement that gains in appetite thereby, though further of possibly work or heat). Denoting this appetite by E{displaystyle E}, one might write

ΔE=W+Q+E.{displaystyle Delta {}E=W+Q+E.}



Internal energy

Internal appetite is a sum of all little forms of appetite of a system. It is a appetite indispensable to emanate a system. It is compared to a intensity energy, e.g., molecular structure, clear structure, and other geometric aspects, as good as a suit of a particles, in form of kinetic energy. Thermodynamics is customarily endangered with changes in inner appetite and not a comprehensive value, that is unfit to establish with thermodynamics alone.[18]

First law of thermodynamics

The initial law of thermodynamics asserts that appetite (but not indispensably thermodynamic giveaway energy) is always conserved[19] and that feverishness upsurge is a form of appetite transfer. For comparable systems, with a well-defined feverishness and pressure, a ordinarily used inference of a initial law is that, for a complement theme customarily to vigour army and feverishness send (e.g., a cylinder-full of gas) though chemical changes, a differential change in a inner appetite of a complement (with a gain in appetite signified by a certain quantity) is given as

dE=TdS−PdV{displaystyle mathrm {d} E=Tmathrm {d} S-Pmathrm {d} V,},

where a initial tenure on a right is a feverishness eliminated into a system, voiced in terms of feverishness T and entropy S (in that entropy increases and a change dS is certain when a complement is heated), and a final tenure on a right palm side is identified as work finished on a system, where vigour is P and volume V (the disastrous pointer regulation given application of a complement requires work to be finished on it and so a volume change, dV, is disastrous when work is finished on a system).

This equation is rarely specific, ignoring all chemical, electrical, nuclear, and gravitational forces, effects such as advection of any form of appetite other than feverishness and pV-work. The ubiquitous plan of a initial law (i.e., charge of energy) is current even in situations in that a complement is not homogeneous. For these cases a change in inner appetite of a closed complement is voiced in a ubiquitous form by

dE=δQ+δW{displaystyle mathrm {d} E=delta Q+delta W}

where δQ{displaystyle delta Q} is a feverishness granted to a complement and δW{displaystyle delta W} is a work practical to a system.

Equipartition of energy

The appetite of a automatic harmonic oscillator (a mass on a spring) is otherwise kinetic and potential. At dual points in a fluctuation cycle it is wholly kinetic, and otherwise during dual other points it is wholly potential. Over a whole cycle, or over many cycles, net appetite is so equally separate between kinetic and potential. This is called equipartition principle; sum appetite of a complement with many degrees of leisure is equally separate among all accessible degrees of freedom.

This element is undeniably critical to bargain a poise of a apportion closely compared to energy, called entropy. Entropy is a bulk of evenness of a placement of appetite between tools of a system. When an removed complement is given some-more degrees of leisure (i.e., given new accessible appetite states that are a same as existent states), afterwards sum appetite spreads over all accessible degrees equally though eminence between “new” and “old” degrees. This mathematical outcome is called a second law of thermodynamics.

See also

  • Book: Energy
  • Energy portal
  • Physics portal
  • Combustion
  • Index of appetite articles
  • Index of call articles
  • Orders of bulk (energy)
  • Transfer energy


  1. ^ Energy (and a units) are mostly tangible in terms of a work they can do. However, technically this is customarily an approximation, given a second law of thermodynamics means a work a complement can do is always reduction than a sum appetite of a system, due to rubbish heat. See: Robert L. Lehrman (1973). “Energy is not a ability to do work” (PDF). The Physics Teacher. 
  2. ^ These examples are only for illustration, as it is not a appetite accessible for work that boundary a opening of a contestant though a appetite outlay of a competitor and a force of a weightlifter. A workman stacking shelves in a supermarket does some-more work (in a earthy sense) than possibly of a athletes, though does it some-more slowly.
  3. ^ Crystals are another instance of rarely systematic systems that exist in nature: in this box too, a sequence is compared with a send of a vast volume of feverishness (known as a hideaway energy) to a surroundings.
  4. ^ Although feverishness is “wasted” appetite for a specific appetite transfer,(see: rubbish heat) it can mostly be harnessed to do useful work in successive interactions. However, a extent appetite that can be “recycled” from such liberation processes is singular by a second law of thermodynamics.
  5. ^ The resource for many perceivable earthy collisions is indeed electromagnetic, though it is unequivocally common to facilitate a communication by ignoring a resource of collision and usually calculate a commencement and finish result.
  6. ^ There are several pointer conventions for this equation. Here, a signs in this equation follow a IUPAC convention.


  1. ^ Kittel, Charles; Kroemer, Herbert (1980-01-15). Thermal Physics. Macmillan. ISBN 9780716710882. 
  2. ^ Benno Maurus Nigg; Brian R. MacIntosh; Joachim Mester (2000). Biomechanics and Biology of Movement. Human Kinetics. p. 12. ISBN 9780736003315. 
  3. ^ a b The Laws of Thermodynamics including clever definitions of energy, giveaway energy, et cetera.
  4. ^ Harper, Douglas. “Energy”. Online Etymology Dictionary. Retrieved May 1, 2007. 
  5. ^ Smith, Crosbie (1998). The Science of Energy – a Cultural History of Energy Physics in Victorian Britain. The University of Chicago Press. ISBN 0-226-76420-6. 
  6. ^ Lofts, G; O’Keeffe D; et al. (2004). “11 — Mechanical Interactions”. Jacaranda Physics 1 (2 ed.). Milton, Queensland, Australia: John Willey Sons Australia Ltd. p. 286. ISBN 0-7016-3777-3. 
  7. ^ The Hamiltonian MIT OpenCourseWare website 18.013A Chapter 16.3 Accessed Feb 2007
  8. ^ “Retrieved on May-29-09”. Retrieved 2010-12-12. 
  9. ^ Bicycle calculator – speed, weight, wattage etc. [1].
  10. ^ Schmidt-Rohr, K (2015). “Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O2“. J. Chem. Educ. 92: 2094–2099. doi:10.1021/acs.jchemed.5b00333. 
  11. ^ Ito, Akihito; Oikawa, Takehisa (2004). “Global Mapping of Terrestrial Primary Productivity and Light-Use Efficiency with a Process-Based Model.” in Shiyomi, M. et al. (Eds.) Global Environmental Change in a Ocean and on Land. pp. 343–58.
  12. ^ “Earth’s Energy Budget”. Retrieved 2010-12-12. 
  13. ^ a b Misner, Thorne, Wheeler (1973). Gravitation. San Francisco: W. H. Freeman. ISBN 0-7167-0344-0.  CS1 maint: Multiple names: authors list (link)
  14. ^ Berkeley Physics Course Volume 1. Charles Kittel, Walter D Knight and Malvin A Ruderman
  15. ^ a b Feynman, Richard (1964). The Feynman Lectures on Physics; Volume 1. U.S.A: Addison Wesley. ISBN 0-201-02115-3. 
  16. ^ “E. Noether’s Discovery of a Deep Connection Between Symmetries and Conservation Laws”. 1918-07-16. Retrieved 2010-12-12. 
  17. ^ “Time Invariance”. Retrieved 2010-12-12. 
  18. ^ I. Klotz, R. Rosenberg, Chemical Thermodynamics – Basic Concepts and Methods, 7th ed., Wiley (2008), p.39
  19. ^ Kittel and Kroemer (1980). Thermal Physics. New York: W. H. Freeman. ISBN 0-7167-1088-9. 

Further reading

  • Alekseev, G. N. (1986). Energy and Entropy. Moscow: Mir Publishers. 
  • Crowell, Benjamin (2011) [2003]. Light and Matter. Fullerton, California: Light and Matter. 
  • Ross, John S. (23 Apr 2002). “Work, Power, Kinetic Energy” (PDF). Project PHYSNET. Michigan State University. 
  • Smil, Vaclav (2008). Energy in inlet and society: ubiquitous energetics of formidable systems. Cambridge, USA: MIT Press. ISBN 0-262-19565-8. 
  • Walding, Richard; Rapkins, Greg; Rossiter, Glenn (1999-11-01). New Century Senior Physics. Melbourne, Australia: Oxford University Press. ISBN 0-19-551084-4. 

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