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The elementary charge is exactly defined since 20 May 2019 by the International System of Units. Prior to this change, the elementary charge was a measured quantity whose magnitude was determined experimentally. This section summarizes these historical experimental measurements.
The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). [1][2] It is equal to the electric charge delivered by a 1 ampere current in 1 second and is defined in terms of the elementary charge e, at about 6.241 509 × 1018 e. [2][1]
Charge is quantized: it comes in integer multiples of individual small units called the elementary charge, e, about 1.602 × 10 −19 C, [1] which is the smallest charge that can exist freely. Particles called quarks have smaller charges, multiples of 1 / 3 e , but they are found only combined in particles that have a charge that is an ...
It is a dimensionless quantity, independent of the system of units used, which is related to the strength of the coupling of an elementary charge e with the electromagnetic field, by the formula 4πε 0 ħcα = e 2. Its numerical value is approximately 0.007 297 352 5643 ≈ 1 / 137.035 999 177 , with a relative uncertainty of 1.6 × 10 ...
Oil drop experiment. The oil drop experiment was performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). [1][2] The experiment took place in the Ryerson Physical Laboratory at the University of Chicago. [3][4][5] Millikan received the Nobel Prize in Physics in 1923. [6]
e. The electron (e−, or β− in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. [ 13 ] Electrons belong to the first generation of the lepton particle family, [ 14 ] and are generally thought to be elementary particles because they have no known components or substructure. [ 1 ]
Robert Andrews Millikan. Robert Andrews Millikan (March 22, 1868 – December 19, 1953) was an American experimental physicist who won the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric effect. Millikan graduated from Oberlin College in 1891 and obtained his doctorate ...
Related to the Faraday constant is the "faraday", a unit of electrical charge. Its use is much less common than of the coulomb, but is sometimes used in electrochemistry. [4] One faraday of charge is the charge of one mole of elementary charges (or of negative one mole of electrons), that is, 1 faraday = F × 1 mol = 9.648 533 212 331 001 84 × ...