AC (Alternating Current)

Alternating Current (green curve). The horizontal axis measures time; the vertical, current or voltage

In alternating current (AC or ac) the movement of electric charge periodically reverses direction. In direct current (DC), the flow of electric charge is only in one direction.

The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage, even though some authors have advised against that usage, pointing out the absurdity of the expanded forms such as alternating current current.

AC is the form in which electric power is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. In these applications, an important goal is often the recovery of information encoded (or modulated) onto the AC signal.