Charge conservation - wikipedia Charge conservation This article is about the conservation of electric charge. For a general theoretical concept, see charge ( physics ). In physics, charge conservation is the principle that electric charge can neither be created nor destroyed. The net quantity of electric charge, the amount of positive charge minus the amount of negative charge in the universe, is always conserved. Charge conservation was first proposed by British scientist William Watson in 1746 and American statesman and scientist Benjamin Franklin in 1747, although the first convincing proof was given by Michael Faraday in 1843. it is now discovered and demonstrated, both here and in Europe, that the Electrical Fire is a real Element, or Species of Matter, not created by the Friction, but collected only. -- Benjamin Franklin, Letter to Cadwallader Colden, 5 June 1747 Charge conservation is a physical law that states that the change in the amount of electric charge in any volume of space is exactly equal to the amount of charge flowing into the volume minus the amount of charge flowing out of the volume. In essence, charge conservation is an accounting relationship between the amount of charge in a region and the flow of charge into and out of that region. Mathematically, we can state the law as a continuity equation : Q ( t 2 ) = Q ( t 1 ) + Q I N − Q O U T. ( displaystyle Q ( t_ ( 2 ) ) =Q ( t_ ( 1 ) ) + Q_ ( \rm ( IN ) ) - Q_ ( \rm ( OUT ) ). ) Q ( t ) is the quantity of electric charge in a specific volume at time t, Q is the amount of charge flowing into the volume between time t and t, and Q is the amount of charge flowing out of the volume during the same time period. This does not mean that individual positive and negative charges can not be created or destroyed. Electric charge is carried by subatomic particles such as electrons and protons, which can be created and destroyed. In particle physics, charge conservation means that in elementary particle reactions that create charged particles, equal numbers of positive and negative particles are always created, keeping the net amount of charge unchanged. Similarly, when particles are destroyed, equal numbers of positive and negative charges are destroyed. Although conservation of charge requires that the total quantity of charge in the universe is constant, it leaves open the question of what that quantity is. Most evidence indicates that the net charge in the universe is zero ; that is, there are equal quantities of positive and negative charge. Contents 1 Formal statement of the law 1.1 Mathematical derivation 2 Connection to gauge invariance 3 Experimental evidence 4 See also 5 Notes 6 Further reading Formal statement of the law See also : Continuity equation In electromagnetic field theory, vector calculus can be used to express the law in terms of charge density ρ ( in coulombs per cubic meter ) and electric current density J ( in amperes per square meter ). This is called the charge continuity equation ∂ ρ ∂ t + ∇ ⋅ J = 0. ( displaystyle ( \frac ( partial \rho ) ( partial t ) ) + \nabla cdot mathbf ( J ) = 0. ) The term on the left is the rate of change of the charge density ρ at a point. The term on the right is the divergence of the current density J at the same point. The equation equates these two factors, which says that the only way for the charge density at a point to change is for a current of charge to flow into or out of the point. This statement is equivalent to a conservation of four - current. Mathematical derivation The net current into a volume is I = − ∫∫ S J ⋅ d S ( displaystyle I = - iint limits _ ( S ) mathbf ( J ) cdot d mathbf ( S ) ) where S = ∂ V is the boundary of V oriented by outward - pointing normals, and dS is shorthand for NdS, the outward pointing normal of the boundary ∂ V. Here J is the current density ( charge per unit area per unit time ) at the surface of the volume. The vector points in the direction of the current. From the Divergence theorem this can be written I = − ∫∫∫ V ( ∇ ⋅ J ) d V ( displaystyle I = - iiint limits _ ( V ) left ( \nabla cdot mathbf ( J ) \right ) dV ) Charge conservation requires that the net current into a volume must necessarily equal the net change in charge within the volume. d q d t = − ∫∫∫ V ( ∇ ⋅ J ) d V ( 1 ) ( displaystyle ( \frac ( dq ) ( dt ) ) = - iiint limits _ ( V ) left ( \nabla cdot mathbf ( J ) \right ) dV qquad qquad ( 1 ) ) The total charge q in volume V is the integral ( sum ) of the charge density in V q = ∫∫∫ V ρ d V ( displaystyle q = iiint limits _ ( V ) \rho dV ) So d q d t = ∫∫∫ V d ρ d t d V ( 2 ) ( displaystyle ( \frac ( dq ) ( dt ) ) = iiint limits _ ( V ) ( \frac ( d \rho ) ( dt ) ) dV qquad qquad qquad quad ( 2 ) ) Equating ( 1 ) and ( 2 ) gives 0 = ∫∫∫ V ( ∂ ρ ∂ t + ∇ ⋅ J ) d V. ( displaystyle 0 = iiint limits _ ( V ) left ( ( \frac ( partial \rho ) ( partial t ) ) + \nabla cdot mathbf ( J ) \right ) dV. ) Since this is true for every volume, we have in general ∂ ρ ∂ t + ∇ ⋅ J = 0. ( displaystyle ( \frac ( partial \rho ) ( partial t ) ) + \nabla cdot mathbf ( J ) = 0. ) Connection to gauge invariance Charge conservation can also be understood as a consequence of symmetry through Noether 's theorem, a central result in theoretical physics that asserts that each conservation law is associated with a symmetry of the underlying physics. The symmetry that is associated with charge conservation is the global gauge invariance of the electromagnetic field. This is related to the fact that the electric and magnetic fields are not changed by different choices of the value representing the zero point of electrostatic potential φ ( displaystyle phi ). However the full symmetry is more complicated, and also involves the vector potential A ( displaystyle mathbf ( A ) ). The full statement of gauge invariance is that the physics of an electromagnetic field are unchanged when the scalar and vector potential are shifted by the gradient of an arbitrary scalar field χ ( displaystyle chi ) : φ ′ = φ − ∂ χ ∂ t A ′ = A + ∇ χ. ( displaystyle phi ' = phi - ( \frac ( partial chi ) ( partial t ) ) qquad qquad mathbf ( A ) ' = mathbf ( A ) + \nabla chi. ) In quantum mechanics the scalar field is equivalent to a phase shift in the wavefunction of the charged particle : ψ ′ = e i χ ψ ( displaystyle psi ' = e ^ ( i chi ) psi ) so gauge invariance is equivalent to the well known fact that changes in the phase of a wavefunction are unobservable, and only changes in the magnitude of the wavefunction result in changes to the probability function ψ 2 ( displaystyle psi ^ ( 2 ) ). This is the ultimate theoretical origin of charge conservation. Gauge invariance is a very important, well established property of the electromagnetic field and has many testable consequences. The theoretical justification for charge conservation is greatly strengthened by being linked to this symmetry. For example, local gauge invariance also requires that the photon be massless, so the good experimental evidence that the photon has zero mass is also strong evidence that charge is conserved. Even if gauge symmetry is exact, however, there might be apparent electric charge non-conservation if charge could leak from our normal 3 - dimensional space into hidden extra dimensions. Experimental evidence Simple arguments rule out some types of charge nonconservation. For example, the magnitude of the elementary charge on positive and negative particles must be extremely close to equal, differing by no more than a factor of 10 for the case of protons and electrons. Ordinary matter contains equal numbers of positive and negative particles, protons and electrons, in enormous quantities. If the elementary charge on the electron and proton were even slightly different, all matter would have a large electric charge and would be mutually repulsive. The best experimental tests of electric charge conservation are searches for particle decays that would be allowed if electric charge is not always conserved. No such decays have ever been seen. The best experimental test comes from searches for the energetic photon from an electron decaying into a neutrino and a single photon : e → ν + γ mean lifetime is greater than 7036208280160000000 ♠ 6.6 × 10 years ( 90 % Confidence Level ), but there are theoretical arguments that such single - photon decays will never occur even if charge is not conserved. Charge disappearance tests are sensitive to decays without energetic photons, other unusual charge violating processes such as an electron spontaneously changing into a positron, and to electric charge moving into other dimensions. The best experimental bounds on charge disappearance are : e → anything mean lifetime is greater than 7032201968640000000 ♠ 6.4 × 10 years ( 68 % CL ) n → p + ν + ν charge non-conserving decays are less than 8 × 10 ( 68 % CL ) of all neutron decays See also Capacitance Charge invariance Conservation Laws and Symmetry Introduction to gauge theory -- includes further discussion of gauge invariance and charge conservation Kirchhoff 's circuit laws -- application of charge conservation to electric circuits Maxwell 's equations Relative charge density Franklin 's electrostatic machine Notes Jump up ^ Heilbron, J.L. ( 1979 ). Electricity in the 17th and 18th centuries : a study of early Modern physics. University of California Press. p. 330. ISBN 0 - 520 - 03478 - 3. Jump up ^ Purrington, Robert D. ( 1997 ). Physics in the Nineteenth Century. Rutgers University Press. p. 33. ISBN 0813524423. Jump up ^ The Papers of Benjamin Franklin. 3. Yale University Press. 1961. p. 142. Jump up ^ S. Orito ; M. Yoshimura ( 1985 ). `` Can the Universe be Charged ? ''. Physical Review Letters. 54 ( 22 ) : 2457 -- 2460. Bibcode : 1985PhRvL... 54.2457 O. doi : 10.1103 / PhysRevLett. 54.2457. Jump up ^ E. Masso ; F. Rota ( 2002 ). `` Primordial helium production in a charged universe ''. Physics Letters B. 545 ( 3 -- 4 ) : 221 -- 225. Bibcode : 2002PhLB... 545... 221M. arXiv : astro - ph / 0201248. doi : 10.1016 / S0370 - 2693 ( 02 ) 02636 - 9. Jump up ^ Bettini, Alessandro ( 2008 ). Introduction to Elementary Particle Physics. UK : Cambridge University Press. pp. 164 -- 165. ISBN 0 - 521 - 88021 - 1. Jump up ^ A.S. Goldhaber ; M.M. Nieto ( 2010 ). `` Photon and Graviton Mass Limits ''. Reviews of Modern Physics. 82 ( 1 ) : 939 -- 979. Bibcode : 2010RvMP... 82... 939G. arXiv : 0809.1003. doi : 10.1103 / RevModPhys. 82.939. ; see Section II. C Conservation of Electric Charge Jump up ^ S.Y. Chu ( 1996 ). `` Gauge - Invariant Charge Nonconserving Processes and the Solar Neutrino Puzzle ''. Modern Physics Letters A. 11 ( 28 ) : 2251 -- 2257. Bibcode : 1996MPLA... 11.2251 C. doi : 10.1142 / S0217732396002241. Jump up ^ S.L. Dubovsky ; V.A. Rubakov ; P.G. Tinyakov ( 2000 ). `` Is the electric charge conserved in brane world ? ''. Journal of High Energy Physics. August ( 8 ) : 315 -- 318. Bibcode : 1979PhLB... 84... 315I. arXiv : hep - ph / 0007179. doi : 10.1016 / 0370 - 2693 ( 79 ) 90048 - 0. Jump up ^ Patrignani, C. et al ( Particle Data Group ) ( 2016 ). `` The Review of Particle Physics '' ( PDF ). Chinese Physics C. IOP Publishing. 40 ( 100001 ). Retrieved March 26, 2017. Jump up ^ Particle Data Group ( May 2010 ). `` Tests of Conservation Laws '' ( PDF ). Journal of Physics G. 37 ( 7A ) : 89 -- 98. Bibcode : 2010JPhG... 37g5021N. doi : 10.1088 / 0954 - 3899 / 37 / 7A / 075021. Jump up ^ Agostini, M. ; et al. ( Borexino Coll. ) ( 2015 ). `` Test of Electric Charge Conservation with Borexino ''. Physical Review Letters. 115 ( 23 ) : 231802. Bibcode : 2015PhRvL. 115w1802A. PMID 26684111. arXiv : 1509.01223. doi : 10.1103 / PhysRevLett. 115.231802. CS1 maint : Multiple names : authors list ( link ) Jump up ^ Back, H.O. ; et al. ( Borexino Coll. ) ( 2002 ). `` Search for electron decay mode e → γ + ν with prototype of Borexino detector ''. Physics Letters B. 525 ( 1 -- 2 ) : 29 -- 40. Bibcode : 2002PhLB... 525... 29B. doi : 10.1016 / S0370 - 2693 ( 01 ) 01440 - X. CS1 maint : Multiple names : authors list ( link ) Jump up ^ L.B. Okun ( 1989 ). `` Comments on Testing Charge Conservation and Pauli Exclusion Principle ''. Comments on Nuclear and Particle Physics. 19 ( 3 ) : 99 -- 116. Jump up ^ R.N. Mohapatra ( 1987 ). `` Possible Nonconservation of Electric Charge ''. Physical Review Letters. 59 ( 14 ) : 1510 -- 1512. Bibcode : 1987PhRvL... 59.1510 M. PMID 10035254. doi : 10.1103 / PhysRevLett. 59.1510. Jump up ^ P. Belli ; et al. ( 1999 ). `` Charge non-conservation restrictions from the nuclear levels excitation of Xe induced by the electron 's decay on the atomic shell ''. Physics Letters B. 465 ( 1 -- 4 ) : 315 -- 322. Bibcode : 1999PhLB... 465... 315B. doi : 10.1016 / S0370 - 2693 ( 99 ) 01091 - 6. This is the most stringent of several limits given in Table 1 of this paper. Jump up ^ Norman, E.B. ; Bahcall, J.N. ; Goldhaber, M. ( 1996 ). `` Improved limit on charge conservation derived from Ga solar neutrino experiments ''. Physical Review. D53 ( 7 ) : 4086 -- 4088. Bibcode : 1996PhRvD... 53.4086 N. doi : 10.1103 / PhysRevD. 53.4086. Further reading Lemay, J.A. Leo ( 2008 ). `` Chapter 2 : Electricity ''. The Life of Benjamin Franklin, Volume 3 : Soldier, Scientist, and Politician. University of Pennsylvania Press. ISBN 978 - 0 - 8122 - 4121 - 1. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Charge_conservation&oldid=793633209 '' Categories : Electromagnetism Conservation laws Hidden categories : All articles with dead external links Articles with dead external links from August 2017 Articles with permanently dead external links CS1 maint : Multiple names : authors list Talk Contents About Wikipedia Беларуская Беларуская ( тарашкевіца ) ‎ Català Deutsch Eesti فارسی Français 한국어 Հայերեն हिन्दी Italiano עברית ქართული Қазақша Latviešu Lietuvių 日本 語 ਪੰਜਾਬੀ Piemontèis Polski Português Русский Shqip Slovenščina Татарча / tatarça Українська 中文 Edit links This page was last edited on 3 August 2017, at 00 : 40. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: who discovered law of conservation of electric charge
Answer: William Watson