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Encyclopedia > Electronvolt

The electronvolt (symbol eV) is a unit of energy. In theoretical physics, where distinctions between mass and energy are not concrete, it is often used also as a unit of mass (AAAS Science journal, 2006). It is the amount of kinetic energy gained by a single unbound electron when it passes through an electrostatic potential difference of one volt, in vacuo. In other words, it is equal to one volt (1 volt = 1 joule per coulomb) times the (unsigned) charge of a single electron. The one-word spelling is the modern recommendation[1], although the use of the earlier electron volt still exists. The kinetic energy of an object is the extra energy which it possesses due to its motion. ... e- redirects here. ... A student demonstrating the effects of electrostatics. ... Josephson junction array chip developed by NIST as a standard volt. ... Look up Vacuum in Wiktionary, the free dictionary. ... Josephson junction array chip developed by NIST as a standard volt. ... The joule (IPA pronunciation: or ) (symbol: J) is the SI unit of energy. ... The coulomb (symbol: C) is the SI unit of electric charge. ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ...


One electronvolt is a very small amount of energy:

1 eV = 1.602 176 53(14)×10−19 J. [2] (or approximately 0.160 aJ)

The unit electronvolt is accepted (but not encouraged) for use with SI. It is widely used in solid state, atomic, nuclear, and particle physics, often with prefixes m, k, M, G or T. 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): To help compare different orders of magnitude we list here energies between 10−19 joules and 10−18 joules (0. ... The joule (IPA pronunciation: or ) (symbol: J) is the SI unit of energy. ... Atto- (symbol a) is an SI prefix to a unit and means that it is 10-18 times this unit. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... Solid-state physics, the largest branch of condensed matter physics, is the study of rigid matter, or solids. ... Atomic physics (or atom physics) is the field of physics that studies atoms as isolated systems comprised of electrons and an atomic nucleus. ... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ... 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. ... 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 submultiple. ... 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. ... Atto- (symbol a) is an SI prefix to a unit and means that it is 10-18 times this unit. ...

"A single atom is such a small thing that to talk about its energy in joules would be inconvenient. 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. This quantity is equal to 96.48538(2) kJ/mol. Ionization energies and other atomic properties are often quoted in electronvolts, especially in older texts. 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 kÄ“me (chem), meaning earth[1]) is the science concerned with the composition, structure, and properties of matter, as well as the... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... To help compare different orders of magnitude we list here energies between 10,000 joules and 100,000 joules. ... The joule per mole (symbol: J·mol-1) is an SI derived unit of energy per amount of material. ... The ionization energy (IE) of an atom or of a molecule is the energy required to strip it of an electron. ...

Contents

Using electronvolts to measure mass

Albert 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). 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. “Einstein” redirects here. ... This article or section is in need of attention from an expert on the subject. ... 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. ... The kilogram or kilogramme (symbol: kg) is the SI base unit of mass. ... The joule (symbol J, also called newton metre, or coulomb volt) is the SI unit of energy and work. ...


For example, an electron and a positron, each with a mass of 0.511 MeV/c², can annihilate to yield 1.022 MeV of energy. The proton has a mass of 0.938 GeV/c², making GeV a very convenient unit of mass for particle physics. The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... 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. ...

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) Category: ...


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 (gigaelectronvolt). [[Category:]] Edwin McMillan and Edward Lofgren on the shielding of the Bevatron. ...


Electronvolts and energy

For comparison:

  • 3.2×10−11 joule or 200 MeV - total energy released in nuclear fission of one U-235 atom (on average; depends on the precise break up)
  • 3.5×10−11 joule or 210 MeV - total energy released in fission of one Pu-239 atom (also on average)
  • Molecular bond energies are on the order of an electronvolt per molecule.
  • The typical atmospheric molecule has a kinetic energy of about 1/40 eV. This corresponds to room temperature.

The joule (IPA pronunciation: or ) (symbol: J) is the SI unit of energy. ... An induced nuclear fission event. ... In chemistry, bond energy (E) is a measure of bond strength in a chemical bond. ... To help compare different orders of magnitude we list here energies between 10−21 joule and 10−20 joule (0. ... Room temperature describes a certain temperature within enclosed space that is uses for various purposes by human beings. ...

Electronvolts and 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~eV}}{lambda}

where h is Planck's constant and c is the speed of light. 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 A commemoration plaque for Max Planck on his discovery of Plancks constant, in front of Humboldt University, Berlin. ... A line showing the speed of light on a scale model of Earth and the Moon, about 1. ...

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

to

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

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


Using electronvolts to measure time and distance

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

  • hbar = 6.582 118 89(26) x 10-16 eV s
  • hbar c = 197.326 960 2(77) eV nm

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. For example, the B0 meson has a mean lifetime of 1.542(16) picoseconds, or a decay width of 4.269(44) x 10-4 eV, and its mean decay length is cτ = 462 μm. 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 of reduction (decay) of the assembly. ... A list of mesons. ... A picosecond is an SI unit of time equal to 10-12 of a second. ...


Electronvolts and temperature

In certain fields, such as plasma physics, it is convenient to use the electronvolt as a unit of temperature. The conversion to kelvins (symbol: uppercase K) is defined by using kB, the Boltzmann constant: A Plasma lamp In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... Ludwig Boltzmann The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. ...

{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. Magnetic confinement fusion is an approach to 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. Retrieved on 2006-07-01.  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)

Year 2006 (MMVI) was a common year starting on Sunday (link displays full 2006 calendar) of the Gregorian calendar. ... is the 182nd day of the year (183rd in leap years) in the Gregorian calendar. ...

See also

This article or section does not cite any references or sources. ... 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. ...

External links


  Results from FactBites:
 
Electronvolt - Wikipedia, the free encyclopedia (378 words)
The electronvolt (symbol eV, or, rarely and incorrectly, ev) is a unit of energy.
It is the amount of kinetic energy gained by a single unbound electron when it passes through an electrostatic potential difference of one volt, in vacuum.
In certain fields, such as plasma physics, it is convenient to use the electronvolt as a unit of temperature.
  More results at FactBites »

 
 

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