Lightning is the electric breakdown of air by strong electric fields, or a plasma, which causes an energy transfer from the electric field to heat, mechanical energy (the random motion of air molecules caused by the heat), and light.

In physics and other sciences, energy (from the Greek ενεργός, energos, "active, working")^[1] is a scalar physical quantity, often represented by the symbol E,^[2] that is used to describe a conserved property of objects and systems of objects. Several different forms, such as kinetic, potential, thermal, electrical, chemical, nuclear, and mass have been defined to explain all known natural phenomena. Image File history File linksMetadata Download high resolution version (2048x3072, 3589 KB) This is a rotated version of Lightning over Oradea Romania. ... Image File history File linksMetadata Download high resolution version (2048x3072, 3589 KB) This is a rotated version of Lightning over Oradea Romania. ... This article needs additional references or sources for verification. ... Look up plasma in Wiktionary, the free dictionary. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another as a result of a difference in temperature. ... This article needs additional references or sources for verification. ... Part of a scientific laboratory at the University of Cologne. ... In physics, a scalar is a simple physical quantity that does not depend on direction, and therefore does not depend on the choice of a coordinate system. ... A physical quantity is either a quantity within physics that can be measured (e. ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... {{Portal|Energy}Potential energy is the energy available within a physical system due to an objects position in conjunction with a conservative force which acts upon it (such as the gravitational force or Coulomb force). ... 1. ... Electrical energy can refer to several closely related things. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Nuclear energy is energy released from the atomic nucleus. ... The rest energy of a particle is its energy when it is not moving relative to a given inertial reference frame. ...

Energy may be transformed from one form to another, but it is never created or destroyed. This principle, the conservation of energy, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.^[3] Conservation of energy states that the total amount of energy in an isolated system remains constant, although it may change forms (for instance, friction turns kinetic energy into thermal energy). ... In thermodynamics, an isolated system, as contrasted with a closed system, is a physical system that does not interact with its surroundings. ... Noethers theorem is a central result in theoretical physics that shows that a conservation law can be derived from any continuous symmetry. ...

Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a passenger in an airplane has zero kinetic energy relative to the airplane, but nonzero kinetic energy relative to the earth. This article or section is in need of attention from an expert on the subject. ...

History

Main articles: History of energy, Timeline of thermodynamics, statistical mechanics, and random processes, and History of physics

Thomas Young - the first to use the term "energy" in the modern sense.

The concept of energy emerged out of the idea of vis viva, which Leibniz defined as the product of the mass of an object and its velocity squared; he believed that total vis viva was conserved. To account for slowing due to friction, Leibniz claimed that heat consisted of the random motion of the constituent parts of matter — a view shared by Isaac Newton, although it would be more than a century until this was generally accepted. In 1807, Thomas Young was the first to use the term "energy", instead of vis viva, in its modern sense.^[4] Gustave-Gaspard Coriolis described "kinetic energy" in 1829 in its modern sense, and in 1853, William Rankine coined the term "potential energy." The word energy seems to appear for the first time in the works of Aristotle. ... A timeline of events related to thermodynamics, statistical mechanics, and random processes. ... Since antiquity, human beings have sought to understand the workings of nature: why unsupported objects drop to the ground, why different materials have different properties, the character of the universe such as the form of the Earth and the behavior of celestial objects such as the Sun and the Moon... Image File history File links Download high resolution version (921x1152, 226 KB) This image is in the public domain because its copyright has expired in the United States and those countries with a copyright term of life of the author plus 100 years or less. ... Image File history File links Download high resolution version (921x1152, 226 KB) This image is in the public domain because its copyright has expired in the United States and those countries with a copyright term of life of the author plus 100 years or less. ... Thomas Young, English scientist Thomas Young (June 13, 1773-May 10, 1829) was an English polymath, contributing to the scientific understanding of vision, light, solid mechanics, energy, physiology, and Egyptology. ... Vis Viva is the principle that the difference between the aggregate work of the accelerating forces of a system and that of the retarding forces is equal to one half the vis viva accumulated or lost in the system while the work is being done. ... It has been suggested that this article be split into multiple articles. ... Sir Isaac Newton (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1726][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... Thomas Young, English scientist Thomas Young (June 13, 1773-May 10, 1829) was an English polymath, contributing to the scientific understanding of vision, light, solid mechanics, energy, physiology, and Egyptology. ... Vis Viva is the principle that the difference between the aggregate work of the accelerating forces of a system and that of the retarding forces is equal to one half the vis viva accumulated or lost in the system while the work is being done. ... Gaspard-Gustave de Coriolis or Gustave Coriolis (May 21, 1792–September 19, 1843), mathematician, mechanical engineer and scientist born in Paris, France. ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... William John Macquorn Rankine (July 2, 1820 - December 24, 1872) was a Scottish engineer and physicist. ... {{Portal|Energy}Potential energy is the energy available within a physical system due to an objects position in conjunction with a conservative force which acts upon it (such as the gravitational force or Coulomb force). ...

It was argued for some years whether energy was a substance (the caloric) or merely a physical quantity, such as momentum. The caloric theory is an obsolete scientific theory that heat consists of a fluid called caloric that flows from hotter to colder bodies. ... In classical mechanics, momentum (pl. ...

William Thomson (Lord Kelvin) amalgamated all of these laws into the laws of thermodynamics, which aided in the rapid development of explanations of chemical processes using the concept of energy by Rudolf Clausius, Josiah Willard Gibbs and Walther Nernst. It also led to a mathematical formulation of the concept of entropy by Clausius, and to the introduction of laws of radiant energy by Jožef Stefan. William Thomson, Archbishop of York, has the same name as this man. ... Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dunamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ... Rudolf Clausius - physicist and mathematician Rudolf Julius Emanuel Clausius (January 2, 1822 – August 24, 1888), was a German physicist and mathematician. ... Josiah Willard Gibbs (February 11, 1839 New Haven – April 28, 1903 New Haven) was one of the very first American theoretical physicists and chemists. ... Walther Nernst. ... Ice melting - classic example of entropy increasing[1] described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice. ... Radiant energy is the energy of electromagnetic waves. ... Joseph Stefan (Slovene Jožef Stefan) (March 24, 1835 – January 7, 1893) was a Slovene physicist, mathematician and poet. ...

During a 1961 lecture^[5] for undergraduate students at the California Institute of Technology, Richard Feynman, a celebrated physics teacher and Nobel Laureate, said this about the concept of energy: The California Institute of Technology (commonly referred to as Caltech)[1] is a private, coeducational university located in Pasadena, California, in the United States. ... Richard Phillips Feynman (May 11, 1918 – February 15, 1988; IPA: ) was an American physicist known for expanding the theory of quantum electrodynamics, the physics of the superfluidity of supercooled liquid helium, and particle theory. ... The Nobel Prizes (pronounced no-BELL or no-bell) are awarded annually to people who have done outstanding research, invented groundbreaking techniques or equipment, or made outstanding contributions to society. ...

Since 1918 it has been known that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time. That is, energy is conserved because the laws of physics do not distinguish between different moments of time (see Noether's theorem). Conservation of energy states that the total amount of energy in an isolated system remains constant, although it may change forms (for instance, friction turns kinetic energy into thermal energy). ... Translation is an activity comprising the interpretation of the meaning of a text in one language — the source text — and the production, in another language, of a new, equivalent text — the target text, or translation. ... Sphere symmetry group o. ... In physics, especially in quantum mechanics, conjugate variables are pairs of variables that share an uncertainty relation. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... Noethers theorem is a central result in theoretical physics that shows that a conservation law can be derived from any continuous symmetry. ...

Energy in various contexts

The concept of energy and its transformations is extremely useful in explaining and predicting most natural phenomena. The direction of transformations in energy (what kind of energy is transformed to what other kind) is often described by entropy (equal energy spread among all available degrees of freedom) considerations, since in practice all energy transformations are permitted on a small scale, but certain larger transformations are not permitted because it is statistically unlikely that energy or matter will randomly move into more concentrated forms or smaller spaces. Ice melting - classic example of entropy increasing[1] described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice. ... Degrees of freedom is a general term used in explaining dependence on parameters, and implying the possibility of counting the number of those parameters. ...

The concept of energy is used often in all fields of science.

In chemistry, energy is that attribute of substance that determines how, when and at what speed it can be converted into another substance or react with other substances.

In biology, the sustenance of life itself is critically dependent on energy transformations; living organisms survive because of exchange of energy within and without. In a living organism chemical bonds are constantly broken and made to make the exchange and transformation of energy possible. These chemical bonds are most often bonds in carbohydrates, including sugars.

In geology and meteorology, continental drift, mountain ranges, volcanos, and earthquakes are phenomena that can be explained in terms of energy transformations in the Earth's interior ^[6]. While meteorological phenomena like wind, rain, hail, snow, lightning, tornadoes and hurricanes, are all a result of energy transformations brought about by solar energy on the planet Earth.

In cosmology and astronomy the phenomena of stars, nova, supernova, quasars and gamma ray bursts are the universe's highest-output energy transformations of matter. All stellar phenomena (including solar activity) are driven by various kinds of energy transformations. Energy in such transformations is either from gravitational collapse of matter (usually molecular hydrogen) into various classes of astronomical objects (stars, black holes, etc.), or from nuclear fusion (of lighter elements, primarily hydrogen).

Chemistry - the study of interactions of chemical substances with one another and energy based on the structure of atoms, molecules and other kinds of aggregrates Chemistry (from Egyptian kēme (chem), meaning earth[1]) is the science concerned with the reactions, transformations and aggregations of matter, as well as accompanying... Water and steam are two different forms of the same chemical substance A chemical substance is any material with a definite chemical composition, no matter where it comes from. ... Biological thermodynamics (Greek: bios = life and logikos = reason + Greek: thermos = heat and dynamics = power) is the study of energy transformation in the biological sciences. ... For other uses, see Life (disambiguation). ... In physics and engineering,energy transformation often termed as energy conversion, is any process of transforming one form of energy to another. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... Carbohydrates (literally hydrates of carbon) are chemical compounds that act as the primary biological means of storing or consuming energy, other forms being fat and protein. ... Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. ... Plates in the crust of the earth, according to the plate tectonics theory Continental drift refers to the movement of the Earths continents relative to each other. ... Lyskamm, 4 527 m, Pennine Alps Blue Ridge Mountains in Shenandoah national park, Virginia A mountain is a landform that extends above the surrounding terrain in a limited area. ... For other uses, see Volcano (disambiguation). ... An earthquake is the result of a sudden release of stored energy in the Earths crust that creates seismic waves. ... In physics and engineering,energy transformation often termed as energy conversion, is any process of transforming one form of energy to another. ... This article does not cite any references or sources. ... Rain is a type of precipitation which forms when separate drops of water fall to the Earths surface from clouds. ... This does not cite any references or sources. ... Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. ... This article needs additional references or sources for verification. ... A tornado in central Oklahoma. ... This article is about weather phenomena. ... Physical cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... Artists conception of a white dwarf star accreting hydrogen from a larger companion A nova (pl. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The image above shows the optical afterglow of gamma ray burst GRB-990123 taken on January 23, 1999. ... In physics and engineering,energy transformation often termed as energy conversion, is any process of transforming one form of energy to another. ... Look up stellar in Wiktionary, the free dictionary. ...

Regarding applications of the concept of energy

Energy is subject to a strict global conservation law; that is, whenever one measures (or calculates) the total energy of a system of particles whose interactions do not depend explicitly on time, it is found that the total energy of the system always remains constant ^[7] In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ...

• The total energy of a system can be subdivided and classified in various ways. For example, it is sometimes convenient to distinguish potential energy (which is a function of coordinates only) from kinetic energy (which is a function of coordinate time derivatives only). It may also be convenient to distinguish gravitational energy, electrical energy, thermal energy, and other forms. These classifications overlap; for instance thermal energy usually consists partly of kinetic and partly of potential energy.
• The transfer of energy can take various forms; familiar examples include work, heat flow, and advection, as discussed below.
• The word "energy" is also used outside of physics in many ways, which can lead to ambiguity and inconsistency. The vernacular terminology is not consistent with technical terminology. For example, the important public-service announcement, "Please conserve energy" uses vernacular notions of "conservation" and "energy" which make sense in their own context but are utterly incompatible with the technical notions of "conservation" and "energy" (such as are used in the law of conservation of energy).^[8].

In classical physics energy is considered a scalar quantity, canonical conjugate to time. In special relativity energy is also a scalar (although not a Lorentz scalar but a time component of the energy-momentum 4-vector).^[9] In other words, energy is invariant with respect to rotations of space, but not invariant with respect to rotations of space-time (= boosts). System (from Latin systēma, in turn from Greek systēma) is a set of entities, real or abstract, comprising a whole where each component interacts with or is related to at least one other component and they all serve a common objective. ... {{Portal|Energy}Potential energy is the energy available within a physical system due to an objects position in conjunction with a conservative force which acts upon it (such as the gravitational force or Coulomb force). ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... For a non-technical overview of the subject, see Calculus. ... Classical physics is physics based on principles developed before the rise of quantum theory, usually including the special theory of relativity and general theory of relativity. ... A pair of variables mathematically defined in such a way that they become Fourier transform duals of one-another, or more generally are related through Pontryagin duality. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... The special theory of relativity was proposed in 1905 by Albert Einstein in his article On the Electrodynamics of Moving Bodies. Some three centuries earlier, Galileos principle of relativity had stated that all uniform motion was relative, and that there was no absolute and well-defined state of rest... In physics a Lorentz scalar is a scalar which is invariant under a Lorentz transformation. ... It has been suggested that this article or section be merged with Momentum#Momentum_in_relativistic_mechanics. ... In relativity, a four-vector is a vector in a four-dimensional real vector space, called Minkowski space, whose components transform like the space and time coordinates (t, x, y, z) under spatial rotations and boosts (a change by a constant velocity to another inertial reference frame). ... Space has been an interest for philosophers and scientists for much of human history. ... In special relativity and general relativity, time and three-dimensional space are treated together as a single four-dimensional pseudo-Riemannian manifold called spacetime. ... The Lorentz transformation (LT), named after its discoverer, the Dutch physicist and mathematician Hendrik Antoon Lorentz (1853-1928), forms the basis for the special theory of relativity, which has been introduced to remove contradictions between the theories of electromagnetism and classical mechanics. ...

Energy transfer

Because energy is strictly conserved and is also locally conserved (wherever it can be defined), it is important to remember that by definition of energy the transfer of energy between the "system" and adjacent regions is work. A familiar example is mechanical work. In simple cases this is written as: In physics, mechanical work is the amount of energy transferred by a force. ...

ΔE = W             (1)

if there are no other energy-transfer processes involved. Here ΔE  is the amount of energy transferred, and W  represents the work done on the system.

More generally, the energy transfer can be split into two categories:

ΔE = W + Q             (2)

where Q  represents the heat flow into the system.

There are other ways in which an open system can gain or lose energy. If mass if counted as energy (as in many relativistic problems) then E must contain a term for mass lost or gained. In chemical systems, energy can be added to a system by means of adding substances with different chemical potentials, which potentials are then extracted (both of these process are illustrated by fueling an auto, a system which gains in energy thereby, without addition of either work or heat). These terms may be added to the above equation, or they can generally be subsumed into a quantity called "energy addition term E" which refers to any type of energy carried over the surface of a control volume or system volume. Examples may be seen above, and many others can be imagined (for example, the kinetic energy of a stream of particles entering a system, or energy from a laser beam adds to system energy, without either being either work-done or heat-added, in the classic senses).

ΔE = W + Q + E             (3)

Where E in this general equation represents other additional advected energy terms not covered by work done on a system, or heat added to it.

Energy is also transferred from potential energy (E_p) to kinetic energy (E_k) and then back to potential energy constantly. This is referred to as conservation of energy. In this closed system, energy can not be created or destroyed, so the initial energy and the final energy will be equal to each other. This can be demonstrated by the following:

E_pi + E_ki = E_pF + E _kF

The equation can then be simplified further since E_p = mgh (mass times acceleration due to gravity times the height) and E_k = 1/2 mv² (half times mass times velocity squared). Then the total amount of energy can be found by adding E_p + E_k = E_total.

Energy and the laws of motion

The Hamiltonian

The total energy of a system is sometimes called the Hamiltonian, after William Rowan Hamilton. The classical equations of motion can be written in terms of the Hamiltonian, even for highly complex or abstract systems. These classical equations have remarkably direct analogs in nonrelativistic quantum mechanics.^[10] In physics and mathematics, Hamiltons equations is the set of differential equations that arise in Hamiltonian mechanics, but also in many other related and sometimes apparently not related areas of science. ... Sir William Rowan Hamilton (August 4, 1805 – September 2, 1865) was an Irish mathematician, physicist, and astronomer who made important contributions to the development of optics, dynamics, and algebra. ...

The Lagrangian

Another energy-related concept is called the Lagrangian, after Joseph Louis Lagrange. This is even more fundamental than the Hamiltonian, and can be used to derive the equations of motion. In non-relativistic physics, the Lagrangian is the kinetic energy minus potential energy. A Lagrangian of a dynamical system, named after Joseph Louis Lagrange, is a function of the dynamical variables and concisely describes the equations of motion of the system. ... Joseph-Louis Lagrange, comte de lEmpire (January 25, 1736 – April 10, 1813; b. ...

Usually, the Lagrange formalism is mathematically more convenient than the Hamiltonian for non-conservative systems (like systems with friction).

Energy and thermodynamics

Internal energy

Internal energy – the sum of all microscopic forms of energy of a system. It is related to the molecular structure and the degree of molecular activity and may be viewed as the sum of kinetic and potential energies of the molecules; it is comprised of the following types of energy:^[11] In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of...

In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... Sensible heat is heat energy that is transported by a body that has a temperature higher than its surroundings via conduction, convection, or both. ... In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during evaporation. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Nuclear energy is energy released from the atomic nucleus. ... Nuclear energy is energy released from the atomic nucleus. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... In thermal physics, heat transfer is the passage of thermal energy from a hot to a cold body. ... Mass transfer is the phrase commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. ... Look up work in Wiktionary, the free dictionary. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... 1. ...

The laws of thermodynamics

According to the second law of thermodynamics, work can be totally converted into heat, but not vice versa. The first law of thermodynamics simply asserts that energy is conserved,^[12] and that heat is included as a form of energy transfer. A commonly-used corollary of the first law is that for a "system" subject only to pressure forces and heat transfer (e.g. a cylinder-full of gas), the change in energy of the system is given by: The second law of thermodynamics is an expression of the universal law of increasing entropy. ... The first law of thermodynamics, a generalized expression of the law of the conservation of energy, states: // Description Essentially, the First Law of Thermodynamics declares that energy is conserved for a closed system, with heat and work being the forms of energy transfer. ... The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin in Canberra, Australia. ...

,

where the first term on the right is the heat transfer, defined in terms of temperature T and entropy S, and the last term on the right hand side is identified as "work" done on the system, where pressure is P and volume V (the negative sign is because we must compress the system to do work on it, so that the volume change dV is negative). Although the standard text-book example, this is very specific, ignoring all chemical, electrical, nuclear, and gravitational forces, effects such as advection, and because it depends on temperature. The most general statement of the first law — i.e. conservation of energy — is valid even in situations in which temperature is undefinable. This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... Ice melting - classic example of entropy increasing[1] described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice. ...

Energy is sometimes expressed as:

,

which is unsatisfactory^[8] because there cannot exist any thermodynamic state functions W or Q that are meaningful on the right hand side of this equation, except perhaps in trivial cases.

Equipartition of energy

The energy of a mechanical harmonic oscillator (a mass on a spring) is alternatively kinetic and potential. At two points in the oscillation cycle it is entirely kinetic, and alternatively at two other points it is entirely potential. Over the whole cycle, or over many cycles net energy is thus equally split between kinetic and potential. This is called equipartition principle - total energy of a system with many degrees of freedom is equally split between all these degrees of freedom. In classical mechanics, a Harmonic oscillator is a system which, when displaced from its equilibrium position, experiences a restoring force proportional to the displacement according to Hookes law: where is a positive constant. ... Kinetic energy (also called vis viva, or living force) is energy possessed by a body by virtue of its motion. ... In physics, a potential may refer to the scalar potential or to the vector potential. ... A cycle (Latin cyclus, from Greek kuklos meaning circle) is anything round, in the physical sense (e. ... In classical statistical mechanics, the equipartition theorem is a general formula that allows average energies of many physical systems to be calculated as a function of temperature. ...

This principle is vitally important to understanding the behavior of a quantity closely related to energy, called entropy. Entropy is a measure of evenness of a distribution of energy between parts of a system. This concept is also related to the second law of thermodynamics which basically states that when an isolated system is given more degrees of freedom (=given new available energy states which are the same as existing states), then energy spreads over all available degrees equally without distinction between "new" and "old" degrees. Ice melting - classic example of entropy increasing[1] described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice. ... In mathematical analysis, distributions (also known as generalized functions) are objects which generalize functions and probability distributions. ... The second law of thermodynamics is an expression of the universal law of increasing entropy. ... An energy level is a quantified stable energy, which a physical system can have; the term is most commonly used in reference to the electron configuration of electrons, in atoms or molecules. ...

Oscillators, phonons, and photons

In an ensemble of unsynchronized oscillators, the average energy is spread equally between kinetic and potential.

In a solid, thermal energy (often referred to as heat) can be accurately described by an ensemble of thermal phonons that act as mechanical oscillators. In this model, thermal energy is equally kinetic and potential. 1. ...

In ideal gas, potential of interaction between particles is essentially delta function - thus all of the energy is kinetic.

Because an electrical oscillator (LC circuit) is analogous to a mechanical oscillator, its energy must be, on average, equally kinetic and potential. It is entirely arbitrary whether the magnetic energy is considered kinetic and the electrical energy considered potential, or vice versa. That is, either the inductor is analogous to the mass while the capacitor is analogous to the spring, or vice versa.

1. By extension of the previous line of thought, in free space the electromagnetic field can be considered an ensemble of oscillators, meaning that radiation energy can be considered equally potential and kinetic. This model is useful, for example, when the electromagnetic Lagrangian is of primary interest and is interpreted in terms of potential and kinetic energy.
2. On the other hand, in the key equation m²c⁴ = E² − p²c², the contribution mc² is called the rest energy, and all other contributions to the energy are called kinetic energy. For a particle that has mass, this implies that the kinetic energy is 0.5p² / m at speeds much smaller than c, as can be proved by writing E = mc² √(1 + p²m ^{− 2}c ^{− 2}) and expanding the square root to lowest order. By this line of reasoning, the energy of a photon is entirely kinetic, because the photon is massless and has no rest energy. This expression is useful, for example, when the energy-versus-momentum relationship is of primary interest.

The two analyses are entirely consistent. The electric and magnetic degrees of freedom in item 1 are transverse to the direction of motion, while the speed in item 2 is along the direction of motion. For non-relativistic particles these two notions of potential versus kinetic energy are numerically equal, so the ambiguity is harmless, but not so for relativistic particles. Radiant energy is the energy of electromagnetic waves. ...

Work and virtual work

Main articles: Mechanics, Mechanical work, Thermodynamics, and Quantum mechanics

Work is roughly force times distance. But more precisely, it is Mechanics (Greek ) is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment. ... In physics, mechanical work is the amount of energy transferred by a force. ... Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dunamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ... Fig. ...

This says that the work (W) is equal to the integral (along a certain path) of the force; for details see the mechanical work article. In physics, force is anything that can cause a massive body to accelerate. ... In physics, mechanical work is the amount of energy transferred by a force. ...

Work and thus energy is frame dependent. For example, consider a ball being hit by a bat. In the center-of-mass reference frame, the bat does no work on the ball. But, in the reference frame of the person swinging the bat, considerable work is done on the ball. Refers to reference frame dependance. ...

Quantum mechanics

In quantum mechanics energy is defined in terms of the energy operator as a time derivative of the wave function. The Schrödinger equation equates energy operator to the full energy of a particle or a system. It thus can be considered as a definition of measurement of energy in quantum mechanics. The Schrödinger equation describes the space- and time-dependence of the wave function of quantum systems. The solution of this equation for bound system is discrete (a set of permitted states, each characterized by an energy level) which results in the concept of quanta. In the solution of the Schrödinger equation for any oscillator (vibrator) and for electromagnetic wave in vacuum, the resulting energy states are related to the frequency by the Planck equation E = hν (where h is the Planck's constant and ν the frequency). In the case of electromagnetic wave these energy states are called quanta of light or photons. The quantum Hamiltonian is the physical state of a system, which may be characterized as a ray in an abstract Hilbert space (or, in the case of ensembles, as a trace class operator with trace 1). ... A wave function is a mathematical tool that quantum mechanics uses to describe any physical system. ... For a non-technical introduction to the topic, please see Introduction to quantum mechanics. ... A wave function is a mathematical tool that quantum mechanics uses to describe any physical system. ... A quantum mechanical system can only be in certain states, so that only certain energy levels are possible. ... In physics quanta is the plural of quantum. ... This article is about Planck, the German physicist. ... A commemoration plaque for Max Planck on his discovery of Plancks constant, in front of Humboldt University, Berlin. ... This article does not cite any references or sources. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ...

Relativity

When calculating kinetic energy (= work to accelerate a mass from zero speed to some finite speed) relativistically - using Lorentz transformations instead of Newtonian mechanics, Einstein discovered unexpected by-product of these calculations to be an energy term which does not vanish at zero speed. He called it rest mass energy - energy which every mass must posess even when being at rest. The amount of energy is directly proportional to the mass of body: In physics, mechanical work is the amount of energy transferred by a force. ... This article or section is in need of attention from an expert on the subject. ... This article does not cite any references or sources. ... The Lorentz transformation (LT), named after its discoverer, the Dutch physicist and mathematician Hendrik Antoon Lorentz (1853-1928), forms the basis for the special theory of relativity, which has been introduced to remove contradictions between the theories of electromagnetism and classical mechanics. ... It has been suggested that this article or section be merged with Classical mechanics. ... Energy E = mc^2 of mass m. ...

E = mc²,

where

m is the mass,

c is the speed of light,

E is the rest mass energy.

For example, consider electron-positron annihilation, in which the rest mass of individual particles is destroyed, but the inertia equivalent of the system of the two particles (its invariant mass) remains (since all energy is associated with mass), and this inertia and invariant mass is carried off by photons which individually are massless, but as a system retain their mass. This is a reversible process - the inverse process is called pair creation - in which the rest mass of particles is created from energy of two (or more) annihilating photons. A line showing the speed of light on a scale model of Earth and the Moon The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic... e- redirects here. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... The invariant mass or intrinsic mass or proper mass or just mass is a measurement or calculation of the mass of an object that is the same for all frames of reference. ... Pair production is a nuclear physics process which occurs where a high-energy photon, generally interacting with an atomic nucleus, produces a particle and an antiparticle. ...

In general relativity,^[9] the stress-energy tensor serves as the source term for the gravitational field, in rough analogy to the way mass serves as the source term in the non-relativistic Newtonian approximation.

It is not uncommon to hear that energy is "equivalent" to mass. It would be more accurate to state that every energy has inertia and gravity equivalent, and because mass is a form of energy, then mass too has inertia and gravity associated with it.

Measurement

There is no absolute measure of energy, because energy is defined as the work that one system does (or can do) on another. Thus, only of the transition of a system from one state into another can be defined and thus measured.

Methods

The methods for the measurement of energy often deploy methods for the measurement of still more fundamental concepts of science, namely mass, distance, radiation, temperature, time, electric charge and electric current. Various meters Measurement is an observation that reduces an uncertainty expressed as a quantity. ... This article or section is in need of attention from an expert on the subject. ... Distance is a numerical description of how far apart objects are at any given moment in time. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ... This article includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... Electric current is the flow (movement) of electric charge. ...

A Calorimeter - An instrument used by physicists to measure energy

Conventionally the technique most often employed is calorimetry, a thermodynamic technique that relies on the measurement of temperature using a thermometer or of intensity of radiation using a bolometer. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... A calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. ... The world’s first ice-calorimeter, used in the winter of 1782-83, by Antoine Lavoisier and Pierre-Simon Laplace, to determine the heat evolved in various chemical changes; calculations which were based on Joseph Black’s prior discovery of latent heat. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... It has been suggested that List of temperature sensors be merged into this article or section. ... Rendition of an imaging bolometer from Los Alamos National Laboratory A bolometer is a device for measuring incident electromagnetic radiation. ...

Units

Main article: Units of energy

Throughout the history of science, energy has been expressed in several different units such as ergs and calories. At present, the accepted unit of measurement for energy is the SI unit of energy, the joule. Because energy is defined via work, the SI unit for energy is the same as the unit of work – the joule (J), named in honour of James Prescott Joule and his experiments on the mechanical equivalent of heat. ... An erg is the unit of energy and mechanical work in the centimetre-gram-second (CGS) system of units, symbol erg. Its name is derived from the Greek word meaning work. The erg is a small unit, equal to a force of one dyne exerted for a distance of one... A calorie is a unit of measurement for energy. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... The joule (IPA pronunciation: or ) (symbol: J) is the SI unit of energy. ...

Forms of energy

Heat, a form of energy, is partly potential energy and partly kinetic energy.

Classical mechanics distinguishes between potential energy, which is a function of the position of an object, and kinetic energy, which is a function of its movement. Both position and movement are relative to a frame of reference, which must be specified: this is often (and originally) an arbitrary fixed point on the surface of the Earth, the terrestrial frame of reference. Some introductory authors^{[citation needed]} attempt to separate all forms of energy in either kinetic or potential: this is not incorrect, but neither is it clear that it is a real simplification, as Feynman points out in the citation below. Download high resolution version (1600x1163, 240 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (1600x1163, 240 KB) Wikipedia does not have an article with this exact name. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another as a result of a difference in temperature. ... {{Portal|Energy}Potential energy is the energy available within a physical system due to an objects position in conjunction with a conservative force which acts upon it (such as the gravitational force or Coulomb force). ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... Classical mechanics is used for describing the motion of macroscopic objects, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars, and galaxies. ... {{Portal|Energy}Potential energy is the energy available within a physical system due to an objects position in conjunction with a conservative force which acts upon it (such as the gravitational force or Coulomb force). ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... This article or section is in need of attention from an expert on the subject. ...

These notions of potential and kinetic energy depend on a notion of length scale. For example, one can speak of macroscopic potential and kinetic energy, which do not include thermal potential and kinetic energy. Also what is called chemical potential energy (below) is a macroscopic notion, and closer examination shows that it is really the sum of the potential and kinetic energy on the atomic and subatomic scale. Similar remarks apply to nuclear "potential" energy and most other forms of energy. This dependence on length scale is non-problematic if the various length scales are decoupled, as is often the case ... but confusion can arise when different length scales are coupled, for instance when friction converts macroscopic work into microscopic thermal energy.

In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... Levers can be used to exert a large force over a small distance at one end by exerting only a small force over a greater distance at the other. ... 1. ... This article needs additional references or sources for verification. ... Electrical energy can refer to several closely related things. ... Dynamo, or Dinamo, may refer to: Dynamo, an electrical generator Dynamo (sports society) of the Soviet Union Operation Dynamo, the 1940 mass evacuation at Dunkirk Dynamo, the rock band based in Belfast Dynamo theory, a theory relating to magnetic fields of celestial bodies Dynamo Open Air, annual heavy metal music... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Synchrotrons are now mostly used for producing monochromatic high intensity X-ray beams; here, the synchrotron is the circular track, off which the beamlines branch. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... An igniting match A match is a consumable tool for producing fire under controlled circumstances on demand. ... Nuclear energy is energy released from the atomic nucleus. ... For the DC Comics Superhero also called Atom Smasher, see Albert Rothstein. ...

Potential energy

Main article: Potential energy

Potential energy, symbols E_p, V or Φ, is defined as the work done against a given force (= work of given force with minus sign) in changing the position of an object with respect to a reference position (often taken to be infinite separation). If F is the force and s is the displacement, {{Portal|Energy}Potential energy is the energy available within a physical system due to an objects position in conjunction with a conservative force which acts upon it (such as the gravitational force or Coulomb force). ... In physics, a net force acting on a body causes that body to accelerate; that is, to change its velocity. ...

with the dot representing the scalar product of the two vectors. In mathematics, the dot product (also known as the scalar product and the inner product) is a function (·) : V × V → F, where V is a vector space and F its underlying field. ... A vector in physics and engineering typically refers to a quantity that has close relationship to the spatial coordinates, informally described as an object with a magnitude and a direction. The word vector is also now used for more general concepts (see also vector and generalizations below), but in this...

The name "potential" energy originally signified the idea that the energy could readily be transferred as work—at least in an idealized system (reversible process, see below). This is not completely true for any real system, but is often a reasonable first approximation in classical mechanics.

The general equation above can be simplified in a number of common cases, notably when dealing with gravity or with elastic forces. Gravity is a force of attraction that acts between bodies that have mass. ...

Gravitational potential energy

Main article: Gravitational potential energy

The gravitational force near the Earth's surface varies very little with the height, h, and is equal to the mass, m, multiplied by the gravitational acceleration, g = 9.81 m/s². In these cases, the gravitational potential energy is given by Potential energy (U, or Ep), a kind of scalar potential, is energy by virtue of matter being able to move to a lower-energy state, releasing energy in some form. ... This article covers the physics of gravitation. ... This article or section is in need of attention from an expert on the subject. ... Gravitational acceleration is the acceleration of an object caused by the force of gravity from another object. ...

E_p,g = mgh

A more general expression for the potential energy due to Newtonian gravitation between two bodies of masses m₁ and m₂, useful in astronomy, is Isaac Newtons theory of universal gravitation (part of classical mechanics) states the following: Every single point mass attracts every other point mass by a force pointing along the line combining the two. ... A giant Hubble mosaic of the Crab Nebula, a supernova remnant Astronomy (also frequently referred to as astrophysics) is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earths atmosphere (such as the cosmic background radiation). ...

,

where r is the separation between the two bodies and G is the gravitational constant, 6.6742(10)×10⁻¹¹ m³kg⁻¹s⁻².^[13] In this case, the reference point is the infinite separation of the two bodies. According to the law of universal gravitation, the attractive force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. ...

Elastic potential energy

Main article: Elastic potential energy

Elastic potential energy is defined as a work needed to compress (or expand) a spring. The force, F, in a spring or any other system which obeys Hooke's law is proportional to the extension or compression, x, The elastic potential energy stored in an elastic string or spring of natural length l and modulus of elasticity λ under an extension of x is given by: This equation is often used in calculations of positions of mechanical equilibrium. ... Springs A spring is a flexible elastic object used to store mechanical energy. ... Hookes law accurately models the physical properties of common mechanical springs for small changes in length. ...

F = − kx

where k is the force constant of the particular spring (or system). In this case, the calculated work becomes Hookes law accurately models the physical properties of common mechanical springs for small changes in length. ...

.

Hooke's law is a good approximation for behaviour of chemical bonds under normal conditions, i.e. when they are not being broken or formed. A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ...

Kinetic energy

Main article: Kinetic energy

Kinetic energy, symbols E_k, T or K, is the work required to accelerate an object to a given speed. Indeed, calculating this work one easily obtains the following: The kinetic energy of an object is the extra energy which it possesses due to its motion. ...

At speeds approaching the speed of light, c, this work must be calculated using Lorentz transformations, which results in the following: A line showing the speed of light on a scale model of Earth and the Moon The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness.[1] It is the speed of all electromagnetic... The Lorentz transformation (LT), named after its discoverer, the Dutch physicist and mathematician Hendrik Antoon Lorentz (1853-1928), forms the basis for the special theory of relativity, which has been introduced to remove contradictions between the theories of electromagnetism and classical mechanics. ...

This equation reduces to the one above it, at small (compared to c) velocity. A mathematical by-product of this work (which is immediately seen in the last equation) is that even at rest a mass has the amount of energy equal to:

E_rest = mc²

This energy is thus called rest mass energy. Energy E = mc^2 of mass m. ...

Thermal energy

Main article: Thermal energy

The general definition of thermal energy, symbols q or Q, is also problematic. A practical definition for small transfers of heat is In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... A rotor of a modern steam turbine, used in a power plant A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical work. ... 1. ... A heat exchanger is a device built for efficient heat transfer from one fluid to another, whether the fluids are separated by a solid wall so that they never mix, or the fluids are directly contacted. ... Electrical energy can refer to several closely related things. ... In electronics, thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal potential difference into electric potential difference. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Blast furnace in Sestao, Spain. ... Nuclear energy is energy released from the atomic nucleus. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... 1. ...

where C_v is the heat capacity of the system. This definition will fail if the system undergoes a phase transition—e.g. if ice is melting to water—as in these cases the system can absorb heat without increasing its temperature. In more complex systems, it is preferable to use the concept of internal energy rather than that of thermal energy (see "Chemical energy" below). To meet Wikipedias quality standards, this article or section may require cleanup. ... In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ... In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of...

Despite the theoretical problems, the above definition is useful in the experimental measurement of energy changes. In a wide variety of situations, it is possible to use the energy released by a system to raise the temperature of another object, e.g. a bath of water. It is also possible to measure the amount of electrical energy required to raise the temperature of the object by the same amount. The calorie was originally defined as the amount of energy required to raise the temperature of one gram of water by 1 °C (approximately 4.1855 J, although the definition later changed), and the British thermal unit was defined as the energy required to heat one gallon (UK) of water by 1 °F (later fixed as 1055.06 J). Electrical energy can refer to several closely related things. ... A calorie is a unit of measurement for energy. ... The British thermal unit (BTU or Btu) is a unit of energy used in the Power, Steam Generation and Heating and Air Conditioning industry globally. ... Fahrenheit is a temperature scale named after the German physicist Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ...

Electrical energy

Main article: Electromagnetism

The electric potential energy of given configuration of charges is defined as the work which must be done against the Coulomb force to rearrange charges from infinite separation to this configuration (or the work done by the Coulomb force separating the charges from this configuration to infinity). For two point-like charges Q₁ and Q₂ at a distance r this work, and hence electric potential energy is equal to: Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... Rotating magnetic field as a sum of magnetic vectors from 3 phase coils An electric motor converts electrical energy into mechanical energy. ... 1. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... Electrical energy can refer to several closely related things. ... Figure 1:Three-phase pole-mounted step-down transformer. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Blue, green and red LEDs. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... This article is about the chemical process. ... Nuclear energy is energy released from the atomic nucleus. ... Synchrotrons are now mostly used for producing monochromatic high intensity X-ray beams; here, the synchrotron is the circular track, off which the beamlines branch. ... The electric potential energy of a body is its potential energy due to electric effects, neglecting other forces (such as gravity). ... Look up work in Wiktionary, the free dictionary. ... In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrical force that one stationary, electrically charged substance of small volume (ideally, a point source) exerts on another. ...

where ε₀ is the electric constant of a vacuum, 10⁷/4πc₀² or 8.854188…×10⁻¹² F/m.^[13] If the charge is accumulated in a capacitor (of capacitance C), the reference configuration is usually selected not to be infinite separation of charges, but vice versa - charges at a very close proximity to each other (so there is zero net charge on each plate of a capacitor). In this case the work and thus the electric potential energy becomes The electric constant () is the permittivity of vacuum, a physical constant, defined by: where: - magnetic constant - speed of light In SI units, the value is exactly expressed by: = 2. ... Capacitors: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ...

If an electric current passes through a resistor, electrical energy is converted to heat; if the current passes through an electric appliance, some of the electrical energy will be converted into other forms of energy (although some will always be lost as heat). The amount of electrical energy due to an electric current can be expressed in a number of different ways: Electric current is the flow (movement) of electric charge. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ...

E = UQ = UIt = Pt = U²t / R

where U is the electric potential difference (in volts), Q is the charge (in coulombs), I is the current (in amperes), t is the time for which the current flows (in seconds), P is the power (in watts) and R is the electric resistance (in ohms). The last of these expressions is important in the practical measurement of energy, as potential difference, resistance and time can all be measured very accurately. Josephson junction array chip developed by NIST as a standard volt. ... The coulomb (symbol: C) is the SI unit of electric charge. ... Current can be measured by a galvanometer, via the deflection of a magnetic needle in the magnetic field created by the current. ... In physics, power (symbol: P) is the rate at which work is performed or energy is transferred. ... The watt (symbol: W) is the SI derived unit of power, equal to one joule per second. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... A multimeter can be used to measure resistance in ohms. ...

Magnetic energy

There is no fundamental difference between magnetic energy and electrical energy: the two phenomena are related by Maxwell's equations. The potential energy of a magnet (of dipole m) in a magnetic field (of flux density B) is defined as the work of magnetic force (actually of magnetic torque) on re-alignment of the vector of the magnetic dipole moment, and is equal: In electromagnetism, Maxwells equations are a set of equations first presented as a distinct group in the later half of the nineteenth century by James Clerk Maxwell. ... Iron filings in a magnetic field generated by a bar magnet A magnet is a material or object that produces a magnetic field. ... In physics, the magnetic moment of an object is a vector relating the aligning torque in a magnetic field experienced by the object to the field vector itself. ... Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges and magnetic dipoles, such as those in electric currents and magnets. ... Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ... Look up work in Wiktionary, the free dictionary. ... Torque applied via an adjustable end wrench Relationship between force, torque, and momentum vectors in a rotating system In physics, torque (or often called a moment) can informally be thought of as rotational force or angular force which causes a change in rotational motion. ...

while the energy stored in a inductor (of inductance L) when current 'I is passing via it is An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ...

.

This second expression forms the basis for superconducting magnetic energy storage. Superconducting magnetic energy storage (SMES) uses superconductivity - the ability of certain materials to conduct electricity without resistance - to store electrical energy. ...

Electromagnetic fields

Calculating work needed to create an electric or magnetic field in unit volume (say, in a capacitor or an inductor) results in the electric and magnetic fields energy densities: In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... This article does not cite any references or sources. ... 1. ... A laundromat in California with solar collectors on the roof. ... Electrical energy can refer to several closely related things. ... A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Nonlinear optics is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization P responds nonlinearly to the electric field E of the light. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... This article needs additional references or sources for verification. ... Nuclear energy is energy released from the atomic nucleus. ... Mößbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. ... Look up work in Wiktionary, the free dictionary. ... Energy density is the amount of energy stored in a given system or region of space per unit volume or per unit mass, depending on the context. ...

and

,

in SI units.

Electromagnetic radiation, such as microwaves, visible light or gamma rays, represents a flow of electromagnetic energy. Applying the above expressions to magnetic and electric components of electromagnetic field both the volumetric density and the flow of energy in e/m field can be calculated. The resulting Poynting vector, which is expressed as Microwaves are electromagnetic waves with wavelengths longer than those of terahertz (THz) frequencies, but relatively short for radio waves. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... This article is about electromagnetic radiation. ... The Poynting vector describes the energy flux (J·m−2·s−1) of an electromagnetic field. ...

in SI units, gives the density of the flow of energy and its direction.

The energy of electromagnetic radiation is quantized (has discrete energy levels). The spacing between these levels is equal to An energy level is a quantified stable energy, which a physical system can have; the term is most commonly used in reference to the electron configuration of electrons, in atoms or molecules. ...

E = hν

where h is the Planck constant, 6.6260693(11)×10⁻³⁴ Js,^[13] and ν is the frequency of the radiation. This quantity of electromagnetic energy is usually called a photon. The photons which make up visible light have energies of 270–520 yJ, equivalent to 160–310 kJ/mol, the strength of weaker chemical bonds. Plancks constant, denoted h, is a physical constant that is used to describe the sizes of quanta. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ...

Chemical energy

Main article: Chemical thermodynamics

Chemical energy is the energy due to associations of atoms in molecules and various other kinds of aggregrates of matter. It may be defined as a work of electric forces during re-arrangement of electric charges, electrons and protons, in the process of aggregration. If the chemical energy of a system decreases during a chemical reaction, the energy can either be released as heat or converted into another form of energy. It is also possible in many cases to increase the chemical energy of a system by converting another form of energy from an external source. For example, Willard Gibbs - founder of chemical thermodynamics In thermodynamics, chemical thermodynamics is the mathematical study of the interrelation of heat and work with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics. ... In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... 1. ... A forest fire Fire is a rapid oxidation process that creates light, heat, smoke, and releases energy in varying intensities. ... Electrical energy can refer to several closely related things. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Photo of a glowworm on a stick. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Vapours of hydrogen chloride in a beaker and ammonia in a test tube meet to form a cloud of a new substance, ammonium chloride A chemical reaction is a process that results in the interconversion of chemical substances. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Matter is the substance of which physical objects are composed. ...

when two hydrogen atoms react to form a dihydrogen molecule, the chemical energy decreases by 724 zJ (the bond energy of the H–H bond);

when the electron is completely removed from a hydrogen atom, forming a hydrogen ion (in the gas phase), the chemical energy increases by 2.18 aJ (the ionization energy of hydrogen).

It is common to quote the changes in chemical energy for one mole of the substance in question: typical values for the change in molar chemical energy during a chemical reaction range from tens to hundreds of kJ/mol. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... In chemistry, bond energy (E) is a measure of bond strength in a chemical bond. ... The ionization energy (IE) of an atom or of a molecule is the energy required to strip it of an electron. ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ...

The chemical energy as defined above is also referred to by chemists as the internal energy, U: technically, this is measured by keeping the volume of the system constant. However, most practical chemistry is performed at constant pressure and, if the volume changes during the reaction (e.g. a gas is given off), a correction must be applied to take account of the work done by or on the atmosphere to obtain the enthalpy, H: A chemist is a scientist who specializes in chemistry. ... In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... The volume of a solid object is the three-dimensional concept of how much space it occupies, often quantified numerically. ... t In thermodynamics and molecular chemistry, the enthalpy or heat content (denoted as H or ΔH, or rarely as χ) is a quotient or description of thermodynamic potential of a system, which can be used to calculate the useful work obtainable from a closed thermodynamic system under constant pressure. ...

ΔH = ΔU + pΔV

A second correction, for the change in entropy, S, must also be performed to determine whether a chemical reaction will take place or not, giving the Gibbs free energy, G: Ice melting - classic example of entropy increasing[1] described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice. ... In thermodynamics, the Gibbs free energy is a thermodynamic potential which measures the useful work obtainable from a closed thermodynamic system at a constant temperature and pressure. ...

ΔG = ΔH − TΔS

These corrections are sometimes negligeable, but often not (especially in reactions involving gases).

Since the industrial revolution, the burning of coal, oil, natural gas or products derived from them has been a socially significant transformation of chemical energy into other forms of energy. the energy "consumption" (one should really speak of "energy transformation") of a society or country is often quoted in reference to the average energy released by the combustion of these fossil fuels: The Industrial Revolution was a major shift of technological, socioeconomic, and cultural conditions that occurred in the late 18th century and early 19th century in some Western countries. ... A combustion reaction taking place in a igniting match Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. ... Coal Coal (IPA: ) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... Synthetic motor oil An oil is any substance that is in a viscous liquid state (oily) at ambient temperatures or slightly warmer, and is both hydrophobic (immiscible with water, literally water fearing) and lipophilic (miscible with other oils, literally fat loving). This general definition includes compound classes with otherwise unrelated... Natural gas is a gaseous fossil fuel consisting primarily of methane but including significant quantities of ethane, butane, propane, carbon dioxide, nitrogen, helium and hydrogen sulfide. ... A combustion reaction taking place in a igniting match Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames. ... Fossil fuels are hydrocarbons, primarily coal and petroleum (fuel oil or natural gas), formed from the fossilized remains of dead plants and animals[1] by exposure to heat and pressure in the Earths crust over hundreds of millions of years[2]. The theory that hydrocarbons were formed from these...

1 tonne of coal equivalent (TCE) = 29 GJ

1 tonne of oil equivalent (TOE) = 41.87 GJ

On the same basis, a tank-full of gasoline (45 litres, 12 gallons) is equivalent to about 1.6 GJ of chemical energy. Another chemically-based unit of measurement for energy is the "tonne of TNT", taken as 4.184 GJ. Hence, burning a tonne of oil releases about ten times as much energy as the explosion of one tonne of TNT: fortunately, the energy is usually released in a slower, more controlled manner. The ton of oil equivalent (TOE) is a unit for measuring energy. ... Gasoline or petrol is a petroleum-derived liquid mixture consisting mostly of hydrocarbons and enhanced with benzene or iso-octane to increase octane ratings, primarily used as fuel in internal combustion engines. ... R-phrases S-phrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ...

Nuclear energy

Main article: Nuclear binding energy

Nuclear potential energy, along with electric potential energy, provides the energy released from nuclear fission and nuclear fusion processes. The result of both these processes are nuclei in which strong nuclear forces bind nuclear particles more strongly and closely. Weak nuclear forces (different from strong forces) provide the potential energy for certain kinds of radioactive decay, such as beta decay. The energy released in nuclear processes is so large that the relativistic change in mass (after the energy has been removed) can be as much as several parts per thousand. Binding energy is the energy required to disassemble a whole into separate parts. ... In physics, mechanical energy describes the potential energy and kinetic energy present in the components of a mechanical system. ... An alpha particle is deflected by a magnetic field Alpha particles or alpha rays are a form of particle radiation which are highly ionizing and have low penetration. ... 1. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ... Electrical energy can refer to several closely related things. ... Beta particles are high-energy electrons emitted by certain types of radioactive nuclei such as potassium-40. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... This article is about electromagnetic radiation. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... Nuclear energy is energy released from the atomic nucleus. ... A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its protons or neutrons or both. ... Nuclear energy is energy released from the atomic nucleus. ... The electric potential energy of a body is its potential energy due to electric effects, neglecting other forces (such as gravity). ... For the generation of electrical power by fission, see Nuclear power plant An induced nuclear fission event. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... The weak nuclear force or weak interaction is one of the four fundamental forces of nature. ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ...

Nuclear particles (nucleons) like protons and neutrons are not destroyed (law of conservation of baryon number) in fission and fusion processes. A few lighter particles may be created or destroyed (example: beta minus and beta plus decay, or electron capture decay), but these minor processes are not important to the immediate energy release in fission and fusion. Rather, fission and fusion release energy when collections of baryons become more tightly bound, and it is the energy associated with a fraction of the mass of the nucleons (but not the whole particles) which appears as the heat and electromagnetic radiation generated by nuclear reactions. This heat and radiation retains the "missing" mass, but the mass is missing only because it escapes in the form of heat and light, which retain the mass and conduct it out of the system where it is not measured. The energy from the Sun, also called solar energy, is an example of this form of energy conversion. In the Sun, the process of hydrogen fusion converts about 4 million metric tons of solar matter per second into light, which is radiated into space, but during this process, the number of total protons and neutrons in the sun does not change. In this system, the light itself retains the inertial equivalent of this mass, and indeed the mass itself (as a system), which represents 4 million tons per second of electromagnetic radiation, moving into space. Each of the helium nuclei which are formed in the process are less massive than the four protons from they were formed, but (to a good approximation), no particles or atoms are destroyed in the process of turning the sun's nuclear potential energy into light. In physics a nucleon is a collective name for two baryons: the neutron and the proton. ... In particle physics, the baryon number is an approximate conserved quantum number. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ... Solar power describes a number of methods of harnessing energy from the light of the sun. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ...

Transformations of energy

Main article: Energy conversion

One form of energy can often be readily transformed into another with the help of a device- for instance, a battery, from chemical energy to electrical energy; a dam: gravitational potential energy to kinetic energy of moving water (and the blades of a turbine) and ultimately to electric energy through an electrical generator. Similarly, in the case of a chemical explosion, chemical potential energy is transformed to kinetic energy and thermal energy in a very short time. Yet another example is that of a pendulum. At its highest points the kinetic energy is zero and the gravitational potential energy is at maximum. At its lowest point the kinetic energy is at maximum and is equal to the decrease of potential energy. If one (unrealistically) assumes that there is no friction, the conversion of energy between these processes is perfect, and the pendulum will continue swinging forever. In physics and engineering, energy conversion is any process of converting energy from one form to another. ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Electrical energy can refer to several closely related things. ... This article does not cite any references or sources. ... Potential energy (U, or Ep), a kind of scalar potential, is energy by virtue of matter being able to move to a lower-energy state, releasing energy in some form. ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... A Siemens steam turbine with the case opened. ... Electrical energy or Electromagnetic energy is a form of energy present in any electric field or magnetic field, or in any volume containing electromagnetic radiation. ... “Dynamo” redirects here. ... This article is concerned solely with chemical explosives. ... In thermodynamics and chemistry, chemical potential, symbolized by μ, is a term introduced in 1876 by the American mathematical physicist Willard Gibbs, which he defined as follows: Gibbs noted also that for the purposes of this definition, any chemical element or combination of elements in given proportions may be considered a... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... 1. ... Simple gravity pendulum assumes no air resistance and no friction of/at the nail/screw. ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... Potential energy (U, or Ep), a kind of scalar potential, is energy by virtue of matter being able to move to a lower-energy state, releasing energy in some form. ... The kinetic energy of an object is the extra energy which it possesses due to its motion. ... {{Portal|Energy}Potential energy is the energy available within a physical system due to an objects position in conjunction with a conservative force which acts upon it (such as the gravitational force or Coulomb force). ... friction is the force that opposes the relative motion or tendency toward such motion of two surfaces in contact. ... Simple gravity pendulum assumes no air resistance and no friction of/at the nail/screw. ...

Energy can be converted into matter and vice versa. The mass-energy equivalence formula E = mc², derived independently by Albert Einstein and Henri Poincaré,^{[citation needed]} quantifies the relationship between mass and rest energy. Since c² is very large relative to ordinary human scales, the conversion of mass to other forms of energy can liberate tremendous amounts of energy, as can be seen in nuclear reactors and nuclear weapons. Conversely, the mass equivalent of a unit of energy is minuscule, which is why loss of energy from most systems is difficult to measure by weight, unless the energy loss is very large. Examples of energy transformation into matter (particles) are found in high energy nuclear physics. Matter is the substance of which physical objects are composed. ... 15ft sculpture of Einsteins 1905 E = mc² formula at the 2006 Walk of Ideas, Germany In physics, mass-energy equivalence is the concept that all mass has an energy equivalence, and all energy has a mass equivalence. ... “Einstein” redirects here. ... Jules TuPac Henri Poincaré (April 29, 1854 – July 17, 1912) (IPA: [][1]) was one of Frances greatest mathematicians and theoretical physicists, and a philosopher of science. ... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ...

In nature, transformations of energy can be fundamentally classed into two kinds: those that are thermodynamically reversible, and those that are thermodynamically irreversible. A reversible process in thermodynamics is one in which no energy is dissipated into empty quantum states available in a volume, from which it cannot be recovered into more concentrated forms (fewer quantum states), without degradation of even more energy. A reversible process is one in which this sort of dissipation does not happen. For example, conversion of energy from one type of potential field to another, is reversible, as in the pendulum system described above. In processes where heat is generated, however, quantum states of lower energy, present as possible exitations in fields between atoms, act as a reservoir for part of the energy, from which it cannot be recovered, in order to be converted with 100% efficiency into other forms of energy. In this case, the energy must partly stay as heat, and cannot be completely recovered as usable energy, except at the price of an increase in some other kind of heat-like increase in disorder in quantum states, in the universe (such as an expansion of matter, or a randomization in a crystal). In thermodynamics, a reversible process (or reversible cycle if the process is cyclic) is a process that can be reversed by means of infinitesimal changes in some property of the system. ... Irreversibility is that property of an event which makes reverting back to the state before the occurrence of the event impossible. ... In thermodynamics, a reversible process (or reversible cycle if the process is cyclic) is a process that can be reversed by means of infinitesimal changes in some property of the system. ...

As the universe evolves in time, more and more of its energy becomes trapped in irreversible states (i.e., as heat or other kinds of increases in disorder). This has been referred to as the inevitable thermodynamic heat death of the universe. In this heat death the energy of the universe does not change, but the fraction of energy which is available to do work, or be transformed to other usable forms of energy, grows less and less. The heat death is a possible final state of the universe, in which it has reached maximum entropy. ... The heat death is a possible final state of the universe, in which it has reached maximum entropy. ...

Law of conservation of energy

Main article: Conservation of energy

Energy is subject to the law of conservation of energy. According to this law, energy can neither be created (produced) nor destroyed itself. It can only be transformed. Conservation of energy states that the total amount of energy in an isolated system remains constant, although it may change forms (for instance, friction turns kinetic energy into thermal energy). ...

Most kinds of energy (with gravitational energy being a notable exception)[1] are also subject to strict local conservation laws, as well. In this case, energy can only be exchanged between adjacent regions of space, and all observers agree as to the volumetric density of energy in any given space. There is also a global law of conservation of energy, stating that the total energy of the universe cannot change; this is a corollary of the local law, but not vice versa.^[5][8] Conservation of energy is the mathematical consequence of translational symmetry of time (=indistinguishability of time intervals taken at different time)^[14] - see Noether's theorem. Conservation of energy states that the total amount of energy in an isolated system remains constant, although it may change forms (for instance, friction turns kinetic energy into thermal energy). ... A translation slides an object by a vector a: Ta(p) = p + a. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... Noethers theorem is a central result in theoretical physics that shows that a conservation law can be derived from any continuous symmetry. ...

According to energy conservation law the total inflow of energy into a system must equal the total outflow of energy from the system, plus the change in the energy contained within the system. For the physical concepts, see conservation of energy and energy efficiency. ...

This law is a fundamental principle of physics. It follows from the translational symmetry of time, a property of most phenomena below the cosmic scale that makes them independent of their locations on the time coordinate. Put differently, yesterday, today, and tomorrow are physically indistinguishable. A translation slides an object by a vector a: Ta(p) = p + a. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ...

Because energy is quantity which is canonical conjugate to time, it is impossible to define exact amount of energy during any finite time interval - making it impossible to apply the law of conservation of energy. This must not be considered a "violation" of the law. We know the law still holds, because a succession of short time periods does not accumulate any violation of conservation of energy. A pair of variables mathematically defined in such a way that they become Fourier transform duals of one-another, or more generally are related through Pontryagin duality. ...

In quantum mechanics energy is expressed using the Hamiltonian operator. On any time scales, the uncertainty in the energy is by Fig. ... In mathematics, an operator is a function that performs some sort of operation on a number, variable, or function. ...

which is similar in form to the uncertainty principle (but not really mathematically equivalent thereto, since H and t are not dynamically conjugate variables, neither in classical nor in quantum mechanics). In quantum physics, the Heisenberg uncertainty principle, sometimes called the Heisenberg indeterminacy principle, expresses a limitation on accuracy of (nearly) simultaneous measurement of observables such as the position and the momentum of a particle. ...

In particle physics, this inequality permits a qualitative understanding of virtual particles which carry momentum, exchange by which with real particles is responsible for creation of all known fundamental forces (more accurately known as fundamental interactions). Virtual photons (which are simply lowest quantum mechanical energy state of photons) are also responsible for electrostatic interaction between electric charges (which results in Coulomb law), for spontaneous radiative decay of exited atomic and nuclear states, for the Casimir force, for van der Waals bond forces and some other observable phenomena. Thousands of particles explode from the collision point of two relativistic (100 GeV per ion) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... In the description of the interaction between elementary particles in quantum field theory, a virtual particle is a temporary elementary particle, used to describe an intermediate stage in the interaction. ... In classical mechanics, momentum (pl. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... This article or section does not cite its references or sources. ... An energy level is a quantified stable energy, which a physical system can have; the term is most commonly used in reference to the electron configuration of electrons, in atoms or molecules. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... Coulombs torsion balance In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrostatic force that one stationary, electrically charged object of small dimensions (ideally, a point source) exerts on another. ... Spontaneous fission (SF) is a form of radioactive decay characteristic of very heavy isotopes, and is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 amu (elements near ruthenium). ... In 1948 Dutch physicist Hendrik B. G. Casimir of Philips Research Labs predicted that two uncharged parallel metal plates will be subject to a force pressing them together. ... In chemistry, the term van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules. ...

Energy and life

Main article: Biological thermodynamics

Any living organism relies on an external source of energy—radiation from the Sun in the case of green plants; chemical energy in some form in the case of animals—to be able to grow and reproduce. The daily 1500–2000 Calories (6–8 MJ) recommended for a human adult are taken in mostly in the form of carbohydrates and fats, of which glucose (C₆H₁₂O₆) and stearin (C₅₇H₁₁₀O₆) are convenient examples. These are oxidised to carbon dioxide and water in the mitochondria Biological thermodynamics (Greek: bios = life and logikos = reason + Greek: thermos = heat and dynamics = power) is the study of energy transformation in the biological sciences. ... A calorie refers to a unit of energy. ... Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... Stearine is a glyceryl ester of stearic acid, derived from animal fats created as a byproduct of processing beef. ... In order to meet Wikipedias quality standards, this article requires cleanup. ... This article describes water from a scientific and technical perspective. ... Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) (from Greek μιτος or mitos, thread + χονδριον or khondrion, granule) is a membrane-enclosed organelle, found in most eukaryotic cells. ...

C₆H₁₂O₆ + 3O₂ → 6CO₂ + 6H₂O

C₅₇H₁₁₀O₆ + 81.5O₂ → 57CO₂ + 55H₂O

and some of the energy is used to convert ADP into ATP Adenosine diphosphate, abbreviated ADP, is a nucleotide. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ...

ADP + HPO₄²⁻ → ATP + H₂O

The rest of the chemical energy in the carbohydrate or fat is converted into heat: the ATP is used as a sort of "energy currency", and some of the chemical energy it contains is used for other metabolism (at each stage of a metabolic pathway, some chemical energy is converted into heat). Only a tiny fraction of the original chemical energy is used for work: consider the examples^[15] A few of the metabolic pathways in a cell. ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ...

gain in kinetic energy of a sprinter during a 100 m race 4 kJ

gain in gravitational potential energy of a 150 kg weight lifted through 2 metres 3kJ

and compare them to the 6–8 MJ daily energy intake (2000 times higher) of a normal adult (not an Olympic athlete)...

It would appear that living organisms are remarkably inefficient (in the physical sense) in their use of the energy they receive (chemical energy or radiation), and it is true that most real machines manage higher efficiencies. However, the energy that is converted to heat serves a vital purpose, as it allows the organism to be highly ordered. The second law of thermodynamics states that energy (and matter) tends to become more evenly spread out across the universe: to concentrate energy (or matter) in one specific place, it is necessary to spread out a greater amount of energy (as heat) across the remainder of the universe ("the surroundings").^[16] Simpler organisms can achieve higher energy efficiencies than more complex ones, but the complex organisms can occupy ecological niches that are not available to their simpler brethren. The conversion of a portion of the chemical energy to heat at each step in a metabolic pathway is the physical reason behind the pyramid of biomass observed in ecology: to take just the first step in the food chain, of the estimated 124.7 Pg/a of carbon that is fixed by photosynthesis, 64.3 Pg/a (52%) are used for the metabolism of green plants,^[17] i.e. reconverted into carbon dioxide and heat. In physics and engineering, including mechanical and electrical engineering, energy efficiency is a dimensionless number, with a value between 0 and 1 or with times 100 given in percent. ... Wind turbines The scientific definition of a machine is any device that transmits or modifies energy. ... The second law of thermodynamics is an expression of the universal law of increasing entropy. ... Two lichenes species on a rock, in two different ecological niches In ecology, a niche is a term describing the relational position of a species or population in an ecosystem. ... This article or section does not cite any references or sources. ... This article or section does not cite any references or sources. ... Carbon fixation is a process found in autotrophs, usually driven by photosynthesis, whereby carbon dioxide is converted into organic compounds. ... This article needs additional references or sources for verification. ...

See also

Image File history File links Portal. ... Image File history File links Portal. ... The sparks generated by striking steel against a flint provide the activation energy to initiate combustion in this Bunsen burner. ... t In thermodynamics and molecular chemistry, the enthalpy or heat content (denoted as H or ΔH, or rarely as χ) is a quotient or description of thermodynamic potential of a system, which can be used to calculate the useful work obtainable from a closed thermodynamic system under constant pressure. ... Energy policy is the manner a given entity (often governmental) has decided to address issues of energy development including energy production, distribution and consumption. ... World power usage in terawatts (TW), 1980-2004. ... The free energy is a measure of the amount of mechanical (or other) work that can be extracted from a system, and is helpful in engineering applications. ... In physics, interaction energy is the contribution to the total energy that is caused by an interaction between the objects being considered. ... In thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the potential energy associated with the vibrational and electric energy of... Vacuum energy is an underlying background energy that exists in space even when devoid of matter (known as free space). ... This article or section does not cite any references or sources. ... In physics, power (symbol: P) is the rate at which work is performed or energy is transferred. ... World renewable energy in 2005 (except 2004 data for items marked* or **). Enlarge image to read exclusions. ... Solar irradiance spectrum at top of atmosphere. ... Ice melting - classic example of entropy increasing[1] described in 1862 by Rudolf Clausius as an increase in the disgregation of the molecules of the body of ice. ... Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dunamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ... Because energy is defined via work, the SI unit for energy is the same as the unit of work – the joule (J), named in honour of James Prescott Joule and his experiments on the mechanical equivalent of heat. ... Energy portal This is a list of energy topics which identifies articles and categories that relate to energy in general. ...

Notes and references

IUPAC logo The International Union of Pure and Applied Chemistry (IUPAC) (Pronounced as eye-you-pack) is an international non-governmental organization established in 1919 devoted to the advancement of chemistry. ... Quantities, Units and Symbols in Physical Chemistry (ISBN 0632035838), also known as the Green Book, edited by I. Mills, et al. ... The International Council for Science (ICSU), formerly called the International Council of Scientific Unions, was founded in 1931 as an international non-governmental organization devoted to international co-operation in the advancement of science. ... CODATA (Committee on Data for Science and Technology) was established in 1966 as an interdisciplinary committee of the International Council of Science (ICSU), formerly the International Council of Scientific Unions. ... Quartz crystal Synthetic bismuth hopper crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms... The lattice energy, or lattice enthalpy, of an ionic solid is a measure of the strength of bonds in that ionic compound. ...

Other books

• Alekseev, G. N. (1986). Energy and Entropy. Moscow: Mir Publishers. 
• Walding, Richard,  Rapkins, Greg,  Rossiter, Glenn (1999-11-01). New Century Senior Physics. Melbourne, Australia: Oxford University Press. ISBN 0-19-551084-4. 

External links

• Conservation of Energy - a chapter from an online textbook
• Work, Power, Kinetic EnergyPDF (399 KiB) on Project PHYSNET
• What does energy really mean? From Physics World
• Compact description of various energy sources. Energy sources and ecology.
• Glossary of Energy Terms
• Energy for kids