Ampere is the basic unit of the international system of units. Original definition: two infinitely long parallel straight lines, separated by one meter in vacuum, pass through equal constant current. When the force acting on each meter of conductor is 2× 10N, the current of each conductor is 10A. Coulomb is derived from ampere unit, and the cross-sectional area of the conductor passes through 1 ampere current in one second, which is 1 coulomb.

Extended data:

Coulomb is the unit of charge, referred to as the library for short, and is expressed by C. The relationship expressed by the basic unit is "second ampere (s a)". It was named in memory of French physicist Charles Augustine de Coulomb (1736 ~ 1806). Coulomb is not the basic unit of the international system of units, but a derivative unit of the international system of units.

In the history of science, Coulomb unit used to have ampere unit, but in textbooks, the definition of Coulomb unit is derived from "two kinds of charges", and then the definition of current is derived from "the directional movement of charges forms current", and then the definition of ampere is introduced.

Ampere was originally defined as one tenth of absolute ampere in cm-g-s system. Its size is determined in this way to ensure that the values derived from other units in the international system of units are more suitable.

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