(physics) a thermodynamic quantity equivalent to the capacity of a physical system to do work; the units of energy are joules or ergs

an electric current that reverses direction sinusoidally

an electric current that flows in one direction steadily

an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes

the portion of power that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction.