working electrode

https://doi.org/10.1351/goldbook.W06686
An electrode that serves as a transducer responding to the excitation signal and the concentration of the substance of interest in the solution being investigated, and that permits the flow of current sufficiently large to effect appreciable changes of bulk composition within the ordinary duration of a measurement.
Source:
Orange Book, 2nd ed., p. 60 (https://media.iupac.org/publications/analytical_compendium/)