Current-carrying means conducting electrical current through a component or circuit. In practice, it describes any part of a device that is actively carrying charge, whether through a wire, trace, inductor, or other conductive path. In the context of electronics, current flow can create heat, magnetic fields, voltage drop, and mechanical vibration.
This matters in cyber security because physical behavior can expose what a device is doing. Current-carrying components may leak clues through sound, power use, or electromagnetic emissions, which defenders can monitor for diagnostics and attackers may try to exploit in side-channel analysis. In the coil-whine example, a current-carrying inductor can vibrate and produce an audible buzz. That makes current flow not just an electrical detail, but a useful signal when investigating device behavior or detecting abnormal hardware activity.