Ampere Ampere The ampere (; symbol: A), often shortened to "amp", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. The International System of Units defines the ampere in terms of other base units by measuring the electromagnetic force between electrical conductors carrying electric current. The earlier CGS measurement system had two different definitions of current, one essentially the same as the SI's and the other using electric charge as the base unit, with the unit of charge defined by
2019 redefinition of SI base units the Avogadro constant, Brian Leonard of the University of Akron, writing in "Metrologia" proposed that the dalton (Da) be redefined such that , but that the unified atomic mass unit () retain its current definition based on the mass of C, ceasing to exactly equal to the dalton. This would result in the dalton and the atomic mass unit potentially differing from each other with a relative uncertainty of the order of 10. However, the draft of the ninth SI Brochure defines both the dalton (Da) and the unified atomic mass unit (u) as exactly 1/12 of the mass of