Galvanic cell bridge zinc ions leave and anions enter the zinc half-cell. In the copper half-cell, the copper ions plate onto the copper electrode (reduction), taking up electrons that leave the external conductor. Since the Cu ions (cations) plate onto the copper electrode, the latter is called the cathode. Correspondingly the zinc electrode is the anode. The electrochemical reaction is: In addition, electrons flow through the external conductor, which is the primary application of the galvanic cell. As discussed under #Cell voltage, the emf of the cell is the difference of the half-cell potentials, a measure of the relative ease of dissolution
Concentration polarization Concentration polarization Concentration polarization is a term used in the scientific fields of electrochemistry and membrane science. In electrochemistry, concentration polarization denotes the part of the polarization of an electrolytic cell resulting from changes in the electrolyte concentration due to the passage of current through the electrode/solution interface. Here "polarization" is understood as the shift of the Electrochemical potential difference across the cell from its equilibrium value. When the term is used in this sense, it is equivalent to “concentration overpotential”. the changes in concentration (emergence of concentration gradients in the solution adjacent to the electrode surface) is the difference