A dry cell is a compact primary electrochemical cell that supplies electrical energy at small currents. Like all electrochemical cells, it gets its electrical energy from an internal chemical reaction. The cell is wrapped in a sheet of zinc, inside which is a carbon rod. The space between the zinc and the carbon is packed with a mixture of moist chemicals. The cell has two contacts: the positive (+) terminal (or cathode) and the negative (-) terminal (or anode).

The anode (-), which is the zinc casing oxidises according to the following half-equation:

Zn(s) → Zn²⁺(aq) + 2e^-

The graphite rod, emersed in the electrolyte paste (containing manganese dioxide, Mn₂O₃) is the cathode (+) and reduces according to the following half-equation:

2MnO₂(s) + 2H⁺(aq) + 2e^- → Mn₂O₃(s) + H₂O(l)