Voltaic Pile

A voltaic pile is a set of individual Galvanic cells placed in series. The voltaic pile, invented by Alessandro Volta in 1800, was the first electric battery. Building on Galvani's 1780s discovery of how a circuit of two metals and a frog's leg can cause the frog's leg to respond, in 1791 Volta demonstrated that when two metals and brine-soaked cloth or cardboard are arranged in a circuit they produce an electric current. In 1800 Volta literally piled up several pairs of alternating copper (or silver) and zinc discs (electrodes) separated by cloth or cardboard soaked in brine (electrolyte) to increase the electrolyte conductivity. When the top and bottom contacts were connected by a wire, an electric current flowed through the voltaic pile and the connecting wire. The strength of the pile is expressed in terms of its electromotive force, or emf, given in volts. Volta characterized the emf of a pair of metals in terms of the difference in their voltages, which he could measure. His theory of contact tension considered that the emf, which drives the electric current through a circuit containing a voltaic cell, occurs at the contact between the two metals.