Volta Invents Electric Battery
In 1800, the Italian physicist Alessandro Volta announced the voltaic pile, the first device able to produce a steady, continuous electric current. Earlier tools such as static generators and Leyden jars could only deliver a brief spark or discharge. Volta's invention gave experimenters a reliable source of current for the first time, and it opened the way to electrochemistry, electromagnetism, and eventually the electrical technologies of the modern world.
The invention grew out of a dispute with another Italian scientist, Luigi Galvani of Bologna. In the 1780s and 1790s, Galvani observed that frog legs twitched when touched with metals, and he concluded that the effect came from a form of "animal electricity" inside the tissue. Volta, a professor at the University of Pavia who had already made his name with work on static electricity and the chemistry of gases, was skeptical. He came to believe that the electricity arose from the contact of two different metals, with the moist animal tissue merely acting as a conductor and detector. To test the idea, he sought a way to amplify the effect.
His solution was a stack of alternating discs of two metals, commonly silver and zinc, separated by cardboard or cloth soaked in brine or acid. Touching the top and bottom of the pile produced a shock, and adding more layers increased the strength. Volta described it in a letter to Joseph Banks, president of the Royal Society in London, and the letter was published in the Society's journal in 1800. He also devised a related arrangement of cups of liquid linked by metal strips, sometimes called the crown of cups.
News spread fast. Within weeks, the English researchers William Nicholson and Anthony Carlisle used a pile to decompose water into hydrogen and oxygen, a landmark in electrolysis. Humphry Davy later used much larger batteries to isolate elements such as sodium and potassium. In 1820, Hans Christian Ørsted's discovery that a current deflects a compass needle, followed by the work of André-Marie Ampère and Michael Faraday, built directly on the availability of steady current. Napoleon, who admired the invention, reportedly honored Volta, who was made a count later in his career.
The scientific question behind the invention was only partly settled in Volta's favor. His contact theory of metals was eventually replaced by the understanding that chemical reactions drive a battery, though Galvani's view of animal electricity also proved right in a different sense, since nerves do use electrical signals. The unit of electric potential, the volt, commemorates Volta. Modern batteries differ greatly in chemistry and scale, but they follow the same principle he demonstrated: two dissimilar materials and an electrolyte can convert chemical energy into a flow of electric charge.