It originated in the Centimetre–gram–second system of units (CGS). The erg is a unit of energy equal to 10 −7 joules (100 nJ). For other uses, see Ergs (disambiguation). Rev.For other uses, see Erg (disambiguation). Hagiwara et al, Review of Particle Physics, Phys.
An in-depth discussion of how the CODATA constants were selected and determined. "CODATA recommended values of the fundamental physical constants: 2002" (PDF). physical constants reference CODATA data.The energy E, frequency f, and wavelength λ of a photon are related byĮ=hf=\frac.įor example, a typical magnetic confinement fusion plasma is 15 keV, or 174 megakelvins. The typical atmospheric molecule has a kinetic energy of about 1/40 eV.Molecular bond energies are on the order of an electronvolt per molecule.3.5 Template:E joule or 210 MeV - total energy released in fission of one Pu-239 atom (also on average).3.2 Template:E joule or 200 MeV - total energy released in nuclear fission of one U-235 atom (on average depends on the precise break up) this is 82 TJ/kg = 20 kt TNT / kg.Since MeV as a unit often are used in nuclear energy equations, for example as in the stellar nuclear fusion process of carbon burning, among others the equationĬonversion of atomic mass unit u to MeV is often performed by the formula: In some older documents, and in the name Bevatron, the symbol "BeV" is used, which stands for "billion-electron-volt" it is equivalent to the GeV. The proton has a mass of 0.938 GeV/c², making GeV (gigaelectronvolt) a very convenient unit of mass for particle physics.ġ eV/c² = 1.783 Template:E kg 1 keV/c² = 1.783 Template:E kg 1 MeV/c² = 1.783 Template:E kg 1 GeV/c² = 1.783 Template:E kg 1 TeV/c² = 1.783 Template:E kg 1 PeV/c² = 1.783 Template:E kg 1 EeV/c² = 1.783 Template:E kg It is thus common in particle physics, where mass and energy are often interchanged, to use eV/ c² or even simply eV as a unit of mass.įor example, an electron and a positron, each with a mass of 0.511 MeV/c², can annihilate to yield 1.022 MeV of energy. Ionization energies and other atomic properties are often quoted in electronvolts, especially in older texts.Īlbert Einstein reasoned that energy is equivalent to mass, as famously expressed in the mass-energy equivalence formula E = mc² (1.0000 kg = 89.876 PJ). This quantity is equal to 96.48538(2) kJ/mol. In chemistry, it is often useful to have the molar equivalent, that is the kinetic energy that would be gained by a mole of electrons passing through a potential difference of one volt. I am sorry that we do that, but that's the way it is for the physicists." But instead of taking a definite unit in the same system, like 10 −20 J, have unfortunately chosen, arbitrarily, a funny unit called an electronvolt (eV). "A single atom is such a small thing that to talk about its energy in joules would be inconvenient. In a recorded lecture from 1961 Richard Feynman apologized to his students for this failure by atomic physicists to use the appropriate SI unit (which would be the attojoule): It is widely used in solid state, atomic, nuclear, and particle physics, often with prefixes m, k, M, G or T. The unit electronvolt is accepted (but not encouraged) for use with SI. One electronvolt is a very small amount of energy:ġ eV = ] J. The one-word spelling is the modern recommendation, although the use of the earlier electron volt still exists. In other words, it is equal to one volt (1 volt = 1 joule per coulomb) times the (unsigned) charge of a single electron. It is the amount of energy equivalent to that gained by a single unbound electron when it is accelerated through an electrostatic potential difference of one volt, in vacuo.
The electronvolt (symbol eV) is a unit of energy. 5 As a measurement for time and distance.
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