What is described as a wire that provides current at a specified voltage level?

The term that describes a wire providing current at a specified voltage level is commonly referred to as a "rail." In electronic and electrical contexts, "rails" are used to designate specific voltage levels that power circuits or components. For example, in power supplies, different rails provide different voltage outputs such as +5V, +12V, or -12V, tailored for various components which require different operating voltages.

The other options do not align with the description of a wire that supplies current at a specified voltage level. "Core" typically refers to the central part of a magnet or wire and is not specifically related to voltage output. "Wire gauge" refers to the thickness of a wire, which affects its current-carrying capacity but does not determine the voltage level. "Lead" usually indicates a wire or connection point, particularly in electronic components, but does not inherently define the provision of current at a specific voltage level. Thus, "rail" is the most appropriate term for identifying a wire that supplies current at a given voltage.