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.
Since it was first measured in Robert Millikan's famous oil-drop experiment in 1909, the elementary charge has been considered indivisible. Quarks, first posited in the 1960s, are believed to have fractional electric charges (in units of e/3), but only to exist in particles with an integer charge. They have never been detected singly. In 1982Robert Laughlin tried to explain the fractional quantum Hall (FQH) effect by predicting the existence of fractionally charged quasiparticles. In 1995 fractional charge of Laughlin quasiparticles has been measured directly in a quantum antidot electrometer at Stony Brook University (New York). In 1997, two groups of physicists at the Weizmann Institute of Science in Rehovot, Israel, and at the CEA laboratory near Paris, claimed to have detected such quasiparticles carrying an electric current.
External links
"Measurement of fractional charge" (Science Report) 1995 (http://www.jstor.org/view/00368075/di002303/00p0036t/0?currentResult=00368075%2bdi002303%2b00p0036t%2b0%2c01%2b19950217%2b9993%2b80049782&searchID=8dd55340.10818876572&frame=noframe&sortOrder=SCORE&userID=81313876@sunysb.edu/018dd55340005010fc7d6&dpi=3&viewContent=Article&config=jstor)
The elementarycharge (e) and the electron mass are examples of constants that characterize the basic, or elementary, particles that constitute matter, such as the electron, alpha particle, proton, neutron, muon, and pion.
The charge and mass of atomic and elementary particles may be expressed in terms of the elementarycharge (e) and the electron mass (m
); the charge of an alpha particle, the nucleus of the helium atom, is given as 2e, whereas the mass of the muon is given as 206.77 m
The interaction between charge and field is the source of one of the four fundamental forces, the electromagnetic force.
The coulomb is defined as the quantity of charge that has passed through the cross-section of a conductor carrying one ampere within one second.
Formally, a measure of charge should be a multiple of the elementarycharge e (charge is quantized), but since it is an average, macroscopic quantity, many orders of magnitude larger than a single elementarycharge, it can effectively take on any real value.
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