The circuit is completed by cations moving to the cathode and anions moving to the anode by ionic conduction. The cell potential can be measured by connecting a high resistance voltmeter across the cell. We can calculate cell potential by Gibbs Free Energy and use the relationship to deduce Nernst Equation too. Nernst equation gives the relationship between the cell potential and the concentrations of the reactants and products. Electrochemical cells are useful in making primary, secondary and fuel cells and the concept of it also helps us to understand the causes of rusting and corrosion which , in turn, makes it easier to find out ways by which we can prevent them.
Electrolysis is a process in which electrical energy is used to produce chemical change.
It is the process of decomposition of electrolytes either in the state of fusion or of solution, when electric current is passed through it. Electrolysis is generally carried out in special vessels called electrolytic cell or voltammeter. The term chemical decomposition implies the mass of ions liberated at the electrodes. Electrolysis can be satisfactorily explained by the theory of ionization . The ions present in the electrolyte solution move toward oppositely charged electrodes when an electric current is flowed through them.