Solution

The total current in the electrolyte, which is contributed by the current of positive ions (cations) and the current of negative ions (anions), is constant throughout the electrolyte and equal to the current through the wires connecting the electrodes (cathode and anode) to the battery. Thus, the amount of substance collected at each electrode is proportional to the total current. (This is known as Faraday's first law of electrolysis.) However, the current of cations and the current of anions vary according to the position in the electrolyte. Near the cathode, almost all of the total current comes from the current of cations, and vice versa. This is consistent with the fact that cations are removed from the electrolyte as they undergo reduction and are collected at the cathode. Similarly, anions are removed from the electrolyte as they undergo oxidation and are collected at the anode.