EMF of a Cell

When the two half-cells of a Daniel cell are connected, a spontaneous redox reaction drives electrons to flow from the anode to the cathode through the external wire. The force behind this directional flow — pushing electrons away from the anode and pulling them toward the cathode — is called the electromotive force (emf) of the cell, also referred to as the cell potential, with the volt (V) as its SI unit.

A cell potential of exactly one volt means that one joule of energy is released for every coulomb of charge that moves between the electrodes:

$1\ \text{J} = 1\ \text{C} \times 1\ \text{V}$ …