Final answer:
The active electrode generally has the greatest current density since it concentrates current into a smaller surface area to fulfill its role in the electrical circuit.
Step-by-step explanation:
The current density at an electrode is determined by how much current is flowing through a unit area of the electrode's surface. Considering the types of electrodes given—active, dispersive, and passive—the one which generally has the greatest current density would be the active electrode. This is because active electrodes are typically designed to concentrate the current into a smaller area, thereby increasing the current density.
Dispersive electrodes, on the other hand, are meant to spread out the current over a larger surface area to reduce the current density and hence reduce the risk of burns or tissue damage during procedures like electrosurgery. Passive electrodes do not actively participate in the electrical circuit's function; they mainly complete the circuit without focusing on the current density.
Situations mentioned like the conduction of electricity in solutions with nonelectrolytes such as ethanol, which do not conduct electricity, and strong electrolytes like KC1, show how the material in contact with the electrodes can influence the overall conductivity and thus relate to how current density can vary based on different conditions and electrode types.