TABLE OF CONTENTS Electric battery cells are devices for generating or storing electric energy by means of electrochemical action. Primary cells are those in which, by chemically transforming one or another of a group of materials, electric energy is generated. The secondary cell is one which, by means of a reversible electrochemical action, converts electric into chemical energy, which is then available to be returned again as electric energy. Such a cell is also called a storage cell. Two or more cells connected, usually in series, constitute a battery. The terminals of a cell are also called poles. The positive terminal or pole is that from which the current flows to the external circuit. The active chemical portions of the cell, connected to the terminals and immersed in the electrolyte, are the electrodes. The electrode connected to the negative terminal of the cell is called the anode because current flows from it into the electrolyte. The electrode into which the current flows in the cell is the cathode. In many primary cells, the anode is metallic zinc. Polarization is a secondary reaction occurring at the surface of one or both of the electrodes, which introduces a back emf and reduces that available at the terminals. A polarized cell, if allowed to stand on open circuit, will regain its normal emf. Depolarizers are means, usually chemical, for preventing polarization.
The development of...
