Vaihtosähkövirta

Vaihtosähkövirta, often abbreviated as AC (Alternating Current), is an electric current which periodically reverses direction. This is in contrast to direct current (DC), where the flow of electric charge is only in one direction. The voltage of an AC circuit also periodically reverses. This characteristic is what defines AC.

The most common form of AC is sinusoidal, meaning its voltage and current vary smoothly and cyclically over time in a sine wave. The frequency of the AC signal indicates how many times the current changes direction per second. In Europe, the standard frequency is 50 Hz, while in North America it is 60 Hz. This frequency determines how many cycles of the sine wave occur each second.

AC is widely used for power transmission because its voltage can be easily stepped up or down using transformers. High voltages are used for long-distance transmission to minimize energy loss, and then these voltages are reduced to safer levels for household and industrial use.

The development and widespread adoption of AC power systems are largely credited to inventors like Nikola Tesla and George Westinghouse, who championed AC over the competing DC systems advocated by Thomas Edison. The advantages of AC in terms of transmission efficiency and voltage transformation were crucial for the electrification of modern society.