amperage

Amperage, commonly referred to as current, is the rate at which electric charges pass a given point in a circuit. It quantifies how much charge flows per second and is measured in amperes (A). Current can be direct (DC) or alternating (AC), and its magnitude determines how much electrical energy devices draw or transmit through conductors.

The ampere is the base unit of electric current in the International System of Units (SI). By definition, one ampere equals one coulomb of charge passing a point each second. The unit is named after André-Marie Ampère, a French physicist who helped establish the science of electrodynamics.

In circuits, current relates to voltage and resistance by Ohm's law: I = V/R. Electrical power is P = VI = I^2R = V^2/R. For alternating current systems, currents are often expressed as root-mean-square (RMS) values, with peak values larger by a factor of √2 for a sinusoidal waveform. This distinction matters for designing and interpreting ratings of components and wiring.

Measuring amperage involves devices such as ammeters placed in series to measure current, or clamp meters that measure current without breaking the circuit. In household wiring, circuits are typically rated by amperage (for example 15 A or 20 A); protective devices (fuses or circuit breakers) limit current to prevent overheating and fires.

In everyday language, amperage is used to mean current, though the precise term is current measured in amperes. Understanding amperage is important for sizing wires, selecting components, and ensuring safe operation of electrical systems.