Clearly, to get energy from the cell, you must get more energy released from the oxidation of the zinc than it takes to reduce the copper. The cell can yield a finite amount of energy from this process, the process being limited by the amount of material available either in the electrolyte or in the metal electrodes. For example, if there were one mole of the sulfate ions SO on the copper side, then the process is limited to transferring two moles of electrons through the external circuit. The amount of electric charge contained in a mole of electrons is called the Faraday constant, and is equal to Avogadro's number times the electron charge:Faraday constant = F = Ne = 6.022 x 10 x 1.602 x 10 = 96,485 Coulombs/moleThe energy yield from a voltaic cell is given by the cell voltage times the number of moles of electrons transferred times the Faraday constant.