ampere

SI unit of electrical current. Electrical current (a flow of negative charge) is measured in a similar way to water current, in terms of an amount per unit time; one ampere (amp) represents a flow of one coulomb per second, which is about 6.28 × 10¹⁸ electrons per second.

When a charge (Q) of one coulomb is flowing at a given point in a material in a time (t) of one second, a current (I) of one ampere is flowing. This can be represented as a formula: Q = I × t. The instrument used to measure the flow of current through a conductor is called an ammeter.

The ampere is defined as the current that produces a specific magnetic force (2 × 10⁻⁷ newtons per metre) between two long, straight, parallel conductors placed 1 m/3.3 ft apart in a vacuum. It is named after the French scientist André Ampère.