Polarisation, Electrolytic. When an electrolyte is decomposed by an electric current, a difference of potential is set up between the anode and cathode which opposes the passage of the current. This represents the force needed to tear apart the molecules of the electrolyte, and is known as the electromotive force of polarisation. If, for instance, water is to be decomposed, at least 1-47 volts are needed; and if, after disconnecting the source of current, the electrodes'of the voltameter are connected to an electrometer, they will be found to differ in potential by that amount. The term is also used to denote an action which occurs in galvanic batteries: hydrogen tends to be deposited in small bubbles on the surface of the positive pole, reducing its effective area, and so diminishing the action of the cell.