Editing Electron (section)

=== Conductivity ===
[[File:Lightning over Oradea Romania cropped.jpg|right|thumb|alt=Four bolts of lightning strike the ground|A [[lightning]] discharge consists primarily of a flow of electrons.<ref>
{{cite book
 | last1 = Rakov
 | first1 = V.A.
 | last2 = Uman
 | first2 = M.A.
 | title = Lightning: Physics and Effects
 | url = https://books.google.com/books?id=TuMa5lAa3RAC&pg=PA4
 | page = 4
 | publisher = Cambridge University Press
 | year = 2007
 | isbn = 978-0-521-03541-5
 | access-date = 2020-08-25
 | archive-date = 2021-01-26
 | archive-url = https://web.archive.org/web/20210126003319/https://books.google.com/books?id=TuMa5lAa3RAC&pg=PA4
 | url-status = live
}}</ref> The electric potential needed for lightning can be generated by a triboelectric effect.<ref>
{{cite journal
 | last1 = Freeman | first1 = G.R.
 | last2 = March | first2 = N.H.
 | year = 1999
 | title = Triboelectricity and some associated phenomena
 | journal = Materials Science and Technology
 | volume = 15 | issue = 12 | pages = 1454–1458
 | doi = 10.1179/026708399101505464
 | bibcode = 1999MatST..15.1454F
}}</ref><ref>
{{cite journal
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 | last2 = Lacks | first2 = D.J.
 | last3 = Sankaran | first3 = R.M.
 | year = 2009
 | title = Methodology for studying particle–particle triboelectrification in granular materials
 | journal = {{ill|Journal of Electrostatics|tr}}
 | volume = 67 | issue = 2–3 | pages = 178–183
 | doi = 10.1016/j.elstat.2008.12.002
}}</ref>]]
If a body has more or fewer electrons than are required to balance the positive charge of the nuclei, then that object has a net electric charge. When there is an excess of electrons, the object is said to be negatively charged. When there are fewer electrons than the number of protons in nuclei, the object is said to be positively charged. When the number of electrons and the number of protons are equal, their charges cancel each other and the object is said to be electrically neutral. A macroscopic body can develop an electric charge through rubbing, by the [[triboelectric effect]].<ref>
{{cite book
 | last = Weinberg | first = S.
 | title = The Discovery of Subatomic Particles
 | url = https://archive.org/details/discoveryofsubat00wein_0/page/15
 | url-access = registration | pages =15–16
 | publisher = Cambridge University Press | year = 2003
 | isbn = 978-0-521-82351-7
}}</ref>

Independent electrons moving in vacuum are termed ''free'' electrons. Electrons in metals also behave as if they were free. In reality the particles that are commonly termed electrons in metals and other solids are quasi-electrons—[[quasiparticle]]s, which have the same electrical charge, spin, and magnetic moment as real electrons but might have a different mass.<ref name="Liang-fu Lou">
{{cite book
 | last = Lou
 | first = L.-F.
 | title = Introduction to phonons and electrons
 | url = https://books.google.com/books?id=XMv-vfsoRF8C&pg=PA162
 | pages = 162, 164
 | publisher = [[World Scientific]]
 | year = 2003
 | isbn = 978-981-238-461-4
 | bibcode = 2003ipe..book.....L
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204071149/https://books.google.com/books?id=XMv-vfsoRF8C&pg=PA162
 | url-status = live
}}</ref> When free electrons – both in vacuum and metals – move, they produce a [[Flow network|net flow]] of charge called an [[electric current]], which generates a magnetic field. Likewise a current can be created by a changing magnetic field. These interactions are described mathematically by [[Maxwell's equations]].<ref>
{{cite book
 | last1 = Guru
 | first1 = B.S.
 | last2 = Hızıroğlu
 | first2 = H.R.
 | title = Electromagnetic Field Theory Fundamentals
 | url = https://archive.org/details/electromagneticf0000bhag
 | pages = 138, 276
 | publisher = Cambridge University Press
 | year = 2004
 | isbn = 978-0-521-83016-4
 | url-access=registration
}}</ref>

At a given temperature, each material has an [[Electrical resistivity and conductivity|electrical conductivity]] that determines the value of electric current when an [[electric potential]] is applied. Examples of good conductors include metals such as copper and gold, whereas glass and [[Polytetrafluoroethylene|Teflon]] are poor conductors. In any [[dielectric]] material, the electrons remain bound to their respective atoms and the material behaves as an [[Insulator (electricity)|insulator]]. Most [[semiconductor]]s have a variable level of conductivity that lies between the extremes of conduction and insulation.<ref>
{{cite book
 | last1 = Achuthan
 | first1 = M.K.
 | last2 = Bhat
 | first2 = K.N.
 | title = Fundamentals of Semiconductor Devices
 | url = https://books.google.com/books?id=REQkwBF4cVoC&pg=PA49
 | pages = 49–67
 | publisher = [[Tata McGraw-Hill]]
 | year = 2007
 | isbn = 978-0-07-061220-4
 | access-date = 2020-08-25
 | archive-date = 2021-01-07
 | archive-url = https://web.archive.org/web/20210107160319/https://books.google.com/books?id=REQkwBF4cVoC&pg=PA49
 | url-status = live
}}</ref> On the other hand, [[metallic bond|metals]] have an [[electronic band structure]] containing partially filled electronic bands. The presence of such bands allows electrons in metals to behave as if they were free or [[delocalized electron]]s. These electrons are not associated with specific atoms, so when an electric field is applied, they are free to move like a gas (called [[Fermi gas]])<ref name="ziman">
{{cite book
 | last = Ziman
 | first = J.M.
 | title = Electrons and Phonons: The Theory of Transport Phenomena in Solids
 | url = https://books.google.com/books?id=UtEy63pjngsC&pg=PA260
 | publisher = Oxford University Press
 | year = 2001
 | page = 260
 | isbn = 978-0-19-850779-6
 | access-date = 2020-08-25
 | archive-date = 2022-02-24
 | archive-url = https://web.archive.org/web/20220224105543/https://books.google.com/books?id=UtEy63pjngsC&pg=PA260
 | url-status = live
}}</ref> through the material much like free electrons.

Because of collisions between electrons and atoms, the [[drift velocity]] of electrons in a conductor is on the order of millimeters per second. However, the speed at which a change of current at one point in the material causes changes in currents in other parts of the material, the [[Wave propagation speed|velocity of propagation]], is typically about 75% of light speed.<ref>
{{cite journal
 | last = Main
 | first = P.
 | date = June 12, 1993
 | title = When electrons go with the flow: Remove the obstacles that create electrical resistance, and you get ballistic electrons and a quantum surprise
 | journal = [[New Scientist]]
 | volume = 1887
 | page = 30
 | url = https://www.newscientist.com/article/mg13818774.500-when-electrons-go-with-the-flow-remove-the-obstacles-thatcreate-electrical-resistance-and-you-get-ballistic-electrons-and-a-quantumsurprise.html
 | access-date = 2008-10-09
 | df = dmy-all
 | archive-date = 2015-02-11
 | archive-url = https://web.archive.org/web/20150211085229/http://www.newscientist.com/article/mg13818774.500-when-electrons-go-with-the-flow-remove-the-obstacles-thatcreate-electrical-resistance-and-you-get-ballistic-electrons-and-a-quantumsurprise.html
 | url-status = live
}}</ref> This occurs because electrical signals propagate as a wave, with the velocity dependent on the [[Relative permittivity|dielectric constant]] of the material.<ref>
{{cite book
 | last = Blackwell
 | first = G.R.
 | title = The Electronic Packaging Handbook
 | url = https://books.google.com/books?id=D0PBG53PQlUC&pg=SA6-PA39
 | pages = 6.39–6.40
 | publisher = [[CRC Press]]
 | year = 2000
 | isbn = 978-0-8493-8591-9
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204083743/https://books.google.com/books?id=D0PBG53PQlUC&pg=SA6-PA39
 | url-status = live
}}</ref>

Metals make relatively good conductors of heat, primarily because the delocalized electrons are free to transport thermal energy between atoms. However, unlike electrical conductivity, the thermal conductivity of a metal is nearly independent of temperature. This is expressed mathematically by the [[Wiedemann–Franz law]],<ref name="ziman" /> which states that the ratio of [[thermal conductivity]] to the electrical conductivity is proportional to the temperature. The thermal disorder in the metallic lattice increases the electrical [[Electrical resistivity and conductivity|resistivity]] of the material, producing a temperature dependence for electric current.<ref name="durrant">
{{cite book
 | last = Durrant
 | first = A.
 | title = Quantum Physics of Matter: The Physical World
 | url = https://books.google.com/books?id=F0JmHRkJHiUC&pg=PA43
 | pages = 43, 71–78
 | publisher = CRC Press
 | year = 2000
 | isbn = 978-0-7503-0721-5
 | access-date = 2015-10-16
 | archive-date = 2016-05-27
 | archive-url = https://web.archive.org/web/20160527150628/https://books.google.com/books?id=F0JmHRkJHiUC&pg=PA43
 | url-status = live
}}</ref>

When cooled below a point called the [[Critical point (thermodynamics)|critical temperature]], materials can undergo a phase transition in which they lose all resistivity to electric current, in a process known as [[superconductivity]]. In [[BCS theory]], pairs of electrons called [[Cooper pair]]s have their motion coupled to nearby matter via lattice vibrations called [[phonon]]s, thereby avoiding the collisions with atoms that normally create electrical resistance.<ref>
{{cite web
 | title = The Nobel Prize in Physics 1972
 | publisher = [[Nobel Foundation|The Nobel Foundation]]
 | year = 2008
 | url = https://nobelprize.org/nobel_prizes/physics/laureates/1972/
 | access-date = 2008-10-13
 | df = dmy-all
 | archive-date = 2008-10-11
 | archive-url = https://web.archive.org/web/20081011050516/http://nobelprize.org/nobel_prizes/physics/laureates/1972/
 | url-status = live
}}</ref> (Cooper pairs have a radius of roughly 100&nbsp;nm, so they can overlap each other.)<ref>
{{cite journal
 | last = Kadin | first = A.M.
 | title = Spatial Structure of the Cooper Pair
 | journal = {{ill|Journal of Superconductivity and Novel Magnetism|tr}}
 | year = 2007
 | volume = 20 | issue = 4 | pages = 285–292
 | arxiv = cond-mat/0510279
 | doi =10.1007/s10948-006-0198-z
 | s2cid = 54948290
}}</ref> However, the mechanism by which [[unconventional superconductor|higher temperature superconductors]] operate remains uncertain.

Electrons inside conducting solids, which are quasi-particles themselves, when tightly confined at temperatures close to [[absolute zero]], behave as though they had split into three other [[quasiparticle]]s: [[spinon]]s, [[orbiton]]s and [[holon (physics)|holons]].<ref>
{{cite web
 | title = Discovery about behavior of building block of nature could lead to computer revolution
 | date = July 31, 2009
 | website = [[Science Daily|ScienceDaily]]
 | url = https://www.sciencedaily.com/releases/2009/07/090730141607.htm
 | access-date = 2009-08-01
 | df = dmy-all
 | archive-date = 2019-04-04
 | archive-url = https://web.archive.org/web/20190404130054/https://www.sciencedaily.com/releases/2009/07/090730141607.htm
 | url-status = live
}}</ref><ref>
{{cite journal
 | last1 = Jompol | first1 = Y.  |display-authors=etal
 | year = 2009
 | title = Probing Spin-Charge Separation in a Tomonaga-Luttinger Liquid
 | journal = [[Science (journal)|Science]]
 | volume = 325 | issue = 5940 | pages = 597–601
 | doi =10.1126/science.1171769
 | pmid =19644117 | bibcode = 2009Sci...325..597J |arxiv = 1002.2782
 | s2cid = 206193
}}</ref> The former carries spin and magnetic moment, the next carries its orbital location while the latter electrical charge.