also called galvanic battery and voltaic battery, a device for generating electricity by chemical action (See ELECTRICITY, subhead Voltaic). The simplest form of an electric battery consists of a tumbler or cup, partially filled with water, to which about a tablespoonful of sulphuric acid has been added, and in which a strip of zinc and a strip of copper have been so placed that they do not touch each other beneath the surface of the liquid. When the strips of metal are joined at their upper ends, either by placing them together or by connecting them with wire, chemical action occurs between the water and the zinc, and electricity is generated. The wires are called poles or electrodes, the one attached to the copper being the positive (+) and that attached to the zinc, the negative (-) electrode. See ELECTRICITY, subhead Positive and Negative. There are various patterns of electric batteries, but in all, the cups or cells are the units for small batteries, and tanks are the units for large batteries. The principle upon which the battery acts is that of having two substances, of different electrical potentiality, immersed in the liquid, upon one of which it acts. One of the most common patterns is the cell used for ringing door bells and operating telephones. This consists of a glass cup, containing a solution of sal ammoniac in water, into which is placed a strip of zinc and a plate of carbon. What is known as a dry battery is made on a similar plan, but the liquid is mixed with starch and glue into a paste, so that it will not spill if the cup is overturned. See BUNSEN'S BATTERY; DANIELL BATTERY.