Difference Between emf and Potential Difference
It is the potential difference between two electrodes when no current is flowing in the circuit.
It is the difference of the electrode potentials of the two electrodes when the cell is under operation.
It is the maximum voltage that the cell can deliver.
It is always less then the maximum value of voltage which the cell can deliver.
It is responsible for the steady flow of current in the cell.
It is not responsible for the steady flow of current in the cell.
Cell EMF and the spontaneity of the reaction : We know,
Nature of reaction
Non – spontaneous