Reference Terms
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Ampere
The ampere (symbol: A) is the SI base unit of electric current equal to one coulomb per second. The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 times 10–7 newton per metre of length. Electric current is the time rate of change or displacement of electric charge. One ampere represents the rate of 1 coulomb of charge per second. The ampere is defined first (it is a base unit, along with the metre, the second, and the kilogram), without reference to the quantity of charge. The unit of charge, the coulomb, is defined to be the amount of charge displaced by a one ampere current in the time of one second.
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December 12, 2025
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