= Solution
In a <galvanic cell>, a spontaneous <oxidation-reduction reaction> supplies electrical work: $\Delta_rG<0$ for discharge, the <anode> is negative, and the <cathode> positive. A discharging <electric battery> and a hydrogen–oxygen <fuel cell> are two practical examples. The first stores its reactants internally; the second is supplied continuously with fuel and oxidant.
An <electrolytic cell> consumes externally supplied electrical <work> to drive electrode reactions or material transfer under an applied potential. Its <anode> is positive and <cathode> negative. <water electrolysis> for hydrogen production and metal <electroplating> are two practical examples. \b[<oxidation> always occurs at the <anode> and <reduction> at the <cathode> in both cell types; the <electrode> signs change.] The <electrolyte> conducts <ions>, while <electrons> flow through the external circuit. A rechargeable <battery> can operate in either regime depending on whether it is discharging or being charged.
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