## Thursday, November 13, 2008

### Ampere

The ampere is a unit of electric current, or amount of electric charge per unit time. The ampere is an SI base unit, and is named after André-Marie Ampère, one of the main discoverers of electromagnetism. One ampere is defined to be the constant current which will produce an attractive force of 2×10–7 newton per meter of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one meter apart in a vacuum. The definition is based on Ampere's force law. The ampere is a base unit, along with the metre, kelvin, second, mole, candela and the kilogram: it is defined without reference to the quantity of electric charge.The SI unit of charge, the coulomb, "is the quantity of electricity carried in 1 second by a current of 1 ampere."

Conversely, an ampere is one coulomb of charge going past a given point in the duration of one second; that is, in general, charge Q is determined by steady current I flowing per unit time t as: Q=It