Elementary charge

Charge carried by one electron

The elementary charge, usually denoted by e, is the magnitude of the charge on an electron and a fundamental physical constant defined to be exactly e = 1.602176634×10−19 C. The elementary charge is a measure of the coupling strength of the electromagnetic force and one of the seven defining constants of the International System of Units (SI). Before being set to a fixed value as part of the 2019 revision of the SI, the elementary charge was viewed as a quantity to be determined experimentally. Robert A. Millikan and Harvey Fletcher's oil drop experiment first directly measured the magnitude of the elementary charge in 1909, differing from the modern accepted value by just 0.6%.

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