|Definition:|| SI unit of electric current, equal to the electric current corresponding to the flow of (1/1,602 176 634) × 1019 elementary electric charges per second
Note 1 to entry: The definition in the SI Brochure is: "The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 1,602 176 634 × 10−19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ΔνCs."
Note 2 to entry: The definition of the ampere in IEV 112-02-07:2010-01 was: "SI unit of electric current, equal to the direct current which, if maintained constant in two straight parallel conductors of infinite length, of circular cross-section with negligible area, and placed 1 metre apart in vacuum, would produce between these conductors a force per length equal to 2 × 10−7 N/m".
Note 3 to entry: The new definition of the ampere fixes the value of the elementary charge e instead of that of the magnetic constant, μ0. As a consequence, the value of μ0 has to be determined experimentally.
Note 4 to entry: The ampere is one of the seven SI base units: second (s), metre (m), kilogram (kg), ampere (A), kelvin (K), mole (mol) and candela (cd).