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Concept
Ampere
Summary
The ampere (ˈæmpɛər , ˈæmpɪər ; symbol: A), often shortened to amp, is the unit of electric current in the International System of Units (SI). One ampere is equal to 1 coulomb, or 6.241509074e18 electrons' worth of charge, moving past a point in a second. It is named after French mathematician and physicist André-Marie Ampère (1775–1836), considered the father of electromagnetism along with Danish physicist Hans Christian Ørsted.
As of the 2019 redefinition of the SI base units, the ampere is defined by fixing the elementary charge to be exactly (coulomb), which means an ampere is an electric current equivalent to e19 elementary charges moving every 1.602176634 seconds or 6.241509074e18 elementary charges moving in a second. Prior to the redefinition the ampere was defined as the current passing through 2 parallel wires 1 metre apart that produces a magnetic force of 2e-7 newtons per metre.
The earlier CGS system has two units of current, one structured similar to the SI's and the other using Coulomb's law as a fundamental relationship, with the unit of charge defined by measuring the force between two charged metal plates. The unit of current is then defined as one unit of charge per second. In SI, the unit of charge, the coulomb, is defined as the charge carried by one ampere during one second.
International System of Electrical and Magnetic Units
The ampere is named for French physicist and mathematician André-Marie Ampère (1775–1836), who studied electromagnetism and laid the foundation of electrodynamics. In recognition of Ampère's contributions to the creation of modern electrical science, an international convention, signed at the 1881 International Exposition of Electricity, established the ampere as a standard unit of electrical measurement for electric current.
The ampere was originally defined as one tenth of the unit of electric current in the centimetre–gram–second system of units. That unit, now known as the abampere, was defined as the amount of current that generates a force of two dynes per centimetre of length between two wires one centimetre apart.
Official source
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