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The electronvolt (symbol eV) is a unit of energy. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός 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 a vacuum. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Electrostatics is the branch of Science that deals with the Phenomena arising from what seems to be stationary Electric charges Since Classical The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. In other words, it is equal to one volt (1 volt = 1 joule per coulomb) multiplied by the (unsigned) charge of a single electron. The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity The coulomb (symbol C) is the SI unit of Electric charge. It is named after Charles-Augustin de Coulomb. The elementary charge, usually denoted e, is the Electric charge carried by a single Proton, or equivalently the negative of the electric charge carried The one-word spelling is the modern recommendation[1], although the use of the earlier electron volt still exists.

One electronvolt is a very small amount of energy:

1 eV = 1.602 176 53(14)×10−19 J. This list compares various energies in Joules (J organized by Order of magnitude. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity [2] (or approximately 0. 160 aJ)

The unit electronvolt is accepted (but not encouraged) for use with SI. atto- (symbol a) is an SI prefix to a unit and means that it is 10−18 times this unit It is widely used in solid state, atomic, nuclear, and particle physics, often with prefixes m, k, M, G or T. Solid-state physics, the largest branch of Condensed matter physics, is the study of rigid Matter, or Solids The bulk of solid-state physics theory and Atomic physics (or atom physics) is the field of Physics that studies atoms as an isolated system of Electrons and an atomic nucleus. Nuclear physics is the field of Physics that studies the building blocks and interactions of Atomic nuclei. Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol to form a Decimal multiple or 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):

A single atom is such a small thing that to talk about its energy in joules would be inconvenient. Richard Phillips Feynman (ˈfaɪnmən May 11 1918 – February 15 1988 was an American Physicist known for the Path integral formulation of quantum atto- (symbol a) is an SI prefix to a unit and means that it is 10−18 times this unit But instead of taking a definite unit in the same system, like 10−20 J, [physicists] have unfortunately chosen, arbitrarily, a funny unit called an electronvolt (eV) . . . I am sorry that we do that, but that's the way it is for the physicists. [3]

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. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this This quantity is equal to 96.48538(2) kJ/mol. This list compares various energies in Joules (J organized by Order of magnitude. The joule per mole (symbol J·mol-1 is an SI derived unit of energy per amount of material Ionization energies and other atomic properties are often quoted in electronvolts, especially in older texts. The ionization potential, ionization energy or EI of an Atom or Molecule is the Energy required to remove an Electron

Contents

As a measurement of mass

Albert Einstein reasoned that energy is equivalent to mass, as famously expressed in the mass-energy equivalence formula E = mc² (1. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object In Physics, mass–energy equivalence is the concept that for particles slower than light any Mass has an associated Energy and vice versa. 0000 kg = 89. 876 PJ). The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity 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.

For example, an electron and a positron, each with a mass of 0. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. 511 MeV/c², can annihilate to yield 1. 022 MeV of energy. The proton has a mass of 0. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive 938 GeV/c², making a GeV/c² a very convenient unit of mass for particle physics. Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them

1 eV/c² = 1. 783×10−36 kg
1 keV/c² = 1. 783×10−33 kg
1 MeV/c² = 1. 783×10−30 kg
1 GeV/c² = 1. 783×10−27 kg
1 TeV/c² = 1. 783×10−24 kg
1 PeV/c² = 1. 783×10−21 kg
1 EeV/c² = 1. 783×10−18 kg

See: Orders of magnitude (mass)

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. To help compare different orders of magnitude, the following list describes various Mass levels between 10&minus36&thinsp kg and 1053&thinspkg The Bevatron was a Particle accelerator &mdash specifically a weak-focusing proton Synchrotron &mdash at Lawrence Berkeley National Laboratory which

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 equation

12C + 12C → 20Ne + 4He + 4. The carbon burning process is a set of Nuclear fusion reactions that take place in massive Stars (at least 4 MSun at birth that have used up Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical 617 MeV

conversion of atomic mass unit u to MeV is often performed by the formula:

1 u = 931. The unified atomic mass unit ( u) or Dalton ( Da) or sometimes universal mass unit, is an unit of Mass used to express 4 MeV

and inversely

1 MeV = 1. 074·10-3 u

Energy

For comparison:

Conversion factor:

Photon properties

The energy E, frequency f, and wavelength λ of a photon are related by

E=hf=\frac{hc}{\lambda}= \frac{1240~\rm{nm}}{\lambda}\rm~eV

where h is Planck's constant and c is the speed of light. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. For example, the spectrum of visible light consists of wavelengths ranging from 400 nm to 700 nm. Photons of visible light therefore have energies ranging from

E_{min} = \frac{1240~\rm{nm}}{700~\rm{nm}}\rm~eV= 1.77~\rm{eV}

to

E_{max} = \frac{1240~\rm{nm}}{400~\rm{nm}}\rm~eV = 3.10~\rm{eV}.

An electronvolt is also the energy of an infrared photon with a wavelength of approximately 1240 nm. Similarly, 10eV would correspond to ultraviolet of wavelength 124 nm, and so on.

As a measurement for time and distance

In particle physics, distances and times are sometimes expressed in inverse electronvolts via the conversion factors[4]

In these units, the mean lifetime τ of an unstable particle can be reexpressed in terms of its decay width Γ (in eV) via \Gamma = \hbar/\tau. Given an assembly of elements the number of which decreases ultimately to zero the lifetime (also called the mean lifetime) is a certain number that characterizes the rate For example, the B0 meson has a mean lifetime of 1. This is a list of known and predicted Mesons. Mesons are made of Quarks and as such are part of the Subatomic particle family called the Hadrons 542(16) picoseconds, or a decay width of 4. To help compare Orders of magnitude of different Times this page lists times between 10&minus12 seconds and 10&minus11 seconds (1 Pico 269(44) x 10-4 eV, and its mean decay length is cτ = 462 μm.

Temperature

In certain fields, such as plasma physics, it is convenient to use the electronvolt as a unit of temperature. In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound The conversion to kelvins (symbol: uppercase K) is defined by using kB, the Boltzmann constant:

{1 \mbox{ eV} \over k_B} = {1.60217653(14) \times 10^{-19} \mbox{J} \over 1.3806505(24) \times 10^{-23} \mbox{J/K}} = 11604.505(20) \mbox{ kelvins}.

For example, a typical magnetic confinement fusion plasma is 15 keV, or 174 megakelvins. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic Bridge from macroscopic to microscopic physics Boltzmann's constant k is a bridge between Macroscopic and microscopic physics Magnetic confinement fusion is an approach to generating Fusion energy that uses Magnetic fields to confine the fusion fuel in the form of a plasma.

References

  1. ^ NIST: Units outside the SI
  2. ^ Peter J. Mohr and Barry N. Taylor (January 2005). "CODATA recommended values of the fundamental physical constants: 2002" (PDF). Reviews of Modern Physics 77: 1–107.   An in-depth discussion of how the CODATA constants were selected and determined.
  3. ^ Transcript of part of a 1961 lecture by Richard Feynman
  4. ^ K. Hagiwara et al, Review of Particle Physics, Phys. Rev. D66, 010001 (2002)

See also

External links

This list compares various energies in Joules (J organized by Order of magnitude. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning "

Dictionary

electronvolt

-noun

  1. (physics) Alternative spelling of electron volt.
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