vaihtovirrälle

Vaihtovirta, often abbreviated as AC from its English counterpart alternating current, is an electric current which periodically reverses direction, in contrast to direct current (DC), which flows only in one direction. The voltage of the waveform also reverses its polarity along with the current. Most electrical power grids worldwide use AC for the transmission of electricity. The primary reason for this is that AC voltages can be easily transformed up or down using transformers, which is crucial for efficient long-distance power transmission.

The waveform of AC is typically sinusoidal, meaning it follows a sine wave pattern over time. This shape is generally produced by rotating electrical machinery. The frequency of the AC, measured in Hertz (Hz), indicates how many cycles of the waveform occur in one second. Common frequencies include 50 Hz and 60 Hz, depending on the region. The instantaneous voltage and current vary continuously throughout the cycle, reaching peak values and then decreasing to zero before reversing.

While sinusoidal AC is most common, other waveforms like square waves and triangular waves can also be generated and used in specific electronic applications. The ability to readily change voltage levels makes AC a highly practical choice for power distribution, allowing for high voltages to be used for transmission, minimizing energy loss, and then stepping down to safer, usable voltages for homes and businesses.