Voltaic Pile
In the late eighteenth century, Italian physician Luigi Galvani found that he could make the muscles of a dissected frog twitch by touching a frog nerve with a scalpel while near an active electrostatic machine, or by placing a copper hook hanging from an iron rail in the animal’s spinal cord. Galvani concluded that there is electricity in the tissues of the frog and other animals.
Alessandro Volta, a scientist who worked not far from Galvani, thought that the “animal electricity” observed by Galvani was actually a phenomenon related to the contact between metals and moist materials. Volta’s work in this area led to his invention, in 1800 of the first electric battery, which came to be widely known as the voltaic pile. He built the device by alternating discs of zinc and copper with pasteboard or leather moistened with brine or vinegar. Each three-disc unit comprised a single electric cell that produced a current due to an electrochemical reaction in which zinc loses electrons and copper gains them.
An example of a voltaic pile is illustrated in this tutorial. As shown, the electric potential of a voltaic pile can be increased by stacking many cells together. To change the number of cells comprising the pile, which is supported by three glass rods mounted on a wooden base, adjust the slider. Observe the effect on the voltmeter as cells are added or removed from the pile to which it is connected by a pair of wires. Notice the cells constructed by Volta each produce about one volt, a measurement of electromotive force that was named in his honor.
Volta’s invention of the pile was a momentous scientific breakthrough, providing the first constant source of electricity and enabling many other advances. In fact, less than two months after Volta described the device in 1800, it was used by William Nicholson and Anthony Carlisle to separate hydrogen and oxygen from water for the first time, marking the foundation of the field of electrochemistry. Many advances in battery technology followed, including, in 1836, the Daniell cell.
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