Alternating Current (AC)｜Glossary

This page is part of the Electrical Glossary for RF and coaxial systems.

Alternating current (AC) is an electric current in which both the direction and magnitude periodically change over time.

AC power is commonly used for commercial electricity supply, typically operating at standard frequencies such as 50 Hz or 60 Hz depending on the region.

AC is suitable for long-distance power transmission because it can be easily transformed to higher or lower voltages, improving efficiency and reducing losses.

In sinusoidal AC systems, values are often expressed as root mean square (RMS), such as Vrms and Irms. Peak values are approximately 1.414 times the RMS value.

In practical applications, factors such as frequency, phase, power factor, and power quality (including noise, voltage dips, and surges) are important considerations.

AC systems often allow polarity-independent connections, but frequency and waveform distortion can affect performance, efficiency, and heat generation.

In RF and coaxial systems, alternating current (AC) is fundamental to signal transmission, as RF signals themselves are high-frequency AC waveforms.

The behavior of AC at high frequencies differs significantly from low-frequency power systems. Effects such as skin effect, impedance, and signal reflections become critical factors.

AC signals in transmission lines must be properly matched to avoid reflections and standing waves, which can degrade signal integrity and increase loss.

Frequency, waveform characteristics, and impedance matching all influence how AC signals propagate through coaxial cables and connectors.

Understanding AC behavior in RF systems is essential for maintaining signal quality, minimizing loss, and ensuring stable system performance.