What defines a galvanic cell?

A galvanic cell is defined by its ability to produce electrical energy through spontaneous redox reactions. The key characteristic of a galvanic cell is that it operates under conditions that allow the overall cell reaction to occur spontaneously, which is indicated by a positive cell potential (or electromotive force, EMF). This spontaneous nature means that the chemical energy stored in the reactants is converted into electrical energy, making it possible to do work in a circuit connected to the cell.

In simpler terms, the spontaneous reactions in a galvanic cell drive the flow of electrons from the anode to the cathode, creating an electric current. A positive cell potential signifies that the Gibbs free energy change for the reaction is negative, confirming that the reaction occurs spontaneously.

In contrast, a system that requires external energy to operate would typically be an electrolytic cell, which is fundamentally different from a galvanic cell. Additionally, the statement regarding energy discharge does not align with the purpose of a galvanic cell since it is specifically designed to discharge energy during spontaneous reactions. Lastly, it is also contrary to the definition of a galvanic cell to have a negative cell potential, as that would indicate that the reaction is not spontaneous under standard conditions.