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
Electrode potential drawing): In case of non-zero net current on the electrode, it is essential to minimize the ohmic IR-drop in the electrolyte, e.g., by positioning the reference electrode near the surface of the working electrode (e.g., see Luggin capillary), or by using a supporting electrolyte of sufficiently high conductivity. The potential measurements are performed with the positive terminal of the electrometer connected to working electrode and the negative terminal to the reference electrode. Historically, two conventions for sign for the electrode potential have formed: In 1953 in Stockholm IUPAC recognized that either of the conventions is permissible; however, it unanimously recommended