What is the difference between cell potential and emf?

Cell potential is the voltage difference between two half-cells in a galvanic cell, while emf is the maximum potential difference of a cell. Understanding the chemical cells involved can provide deeper insight into how these voltages are generated.

Cell potential, also known as electrode potential, is a measure of the voltage difference between two half-cells in a galvanic cell. It is determined by the difference in reduction potentials of the two half-reactions involved in the cell. The cell potential is a measure of the energy per unit charge which is available from the redox reaction to drive the reaction. It is measured in volts (V) and can be either positive or negative. A positive cell potential indicates a spontaneous reaction, while a negative cell potential indicates a non-spontaneous reaction. The concept of equipotential surfaces can further elucidate the distribution of potential around the electrodes.

On the other hand, electromotive force (emf) is the maximum potential difference between the two electrodes of a cell when no current is flowing. It is essentially the 'push' that drives electrons from the anode to the cathode in the cell. The emf of a cell is determined by the nature of the chemical reactions occurring in the cell. It is also measured in volts (V). However, unlike cell potential, emf is always a positive value. This is because it is defined as the work done per unit charge, from the anode to the cathode, against the electric field. Differences between emf vs terminal voltage can provide practical examples of these concepts in action.

In summary, while both cell potential and emf are measures of potential difference in a cell, they are used in different contexts. Cell potential is a measure of the energy available from a redox reaction, and can be either positive or negative depending on the spontaneity of the reaction. Emf, on the other hand, is a measure of the maximum 'push' that drives electrons from the anode to the cathode, and is always a positive value. For a practical application and further study, the role of batteries in circuits can serve as an excellent case study in observing these principles in real-world settings.