Electrode reaction cannot be reversed, and the identities of the anode and cathode are therefore fixed. The anode is always the negative electrode. The cell can be discharged but not recharged. A secondary cell, for example a rechargeable battery, is a cell in which the chemical reactions are reversible. When the cell is being charged, the anode becomes the positive (+) and the cathode the negative (−) electrode. This is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a primary cell, with the anode as the negative and the cathode as the positive
Silver chloride electrode bond with silver of the electrode resulting in silver chloride and free electrons to deliver to the lead wire. The reaction allows current to pass from electrolyte to electrode and the electron current passes through the lead wire for the instrument to read. When there is an uneven distribution of cations and anions, there will be a small voltage called "half-cell potential" associated with the current. In the DC system that is used by the ECG and EEG instruments, the difference between the half-cell potential and the zero potential is shown as DC offset which is an undesirable characteristic. Silver/silver