Faraday Converts Magnetic Force into Electricity

Date October, 1831

By converting magnetic force into electricity through careful experiments, Michael Faraday reinforced the belief of scientists in a field theory that would explain the relationships among light, electricity, and magnetism and helped to make possible the development of modern electric generators.

Locale London, England

Key Figures

• Michael Faraday (1791-1867), British scientist who became director of the Royal Institution laboratory in 1825
• André-Marie Ampère (1775-1836), French scientist who studied the connection between electricity and magnetism
• Sir Humphry Davy (1778-1829), British scientist and director of London’s Royal Institution
• Hans Christian Ørsted (1777-1851), Danish scientist who sought to find a connection between electricity and magnetism
• James Clerk Maxwell (1831-1879), Scottish physicist who extended Faraday’s work

Summary of Event

Early in the nineteenth century, scientists who studied heat, light, electricity, and magnetism sought unifying features that would link these phenomena together. They did so because their experimental evidence contradicted the established principles of Newtonian science, which treated these phenomena as separate and distinct subjects acting as straight-line forces between centers of bodies. The experiments of nineteenth century scientists suggested that these forces exerted their influence as waves acting through some medium. With this evidence, physicists began to think in terms of a field of forces rather than straight-line effects. This growing belief in a field theory benefited from the influential nineteenth century German Naturphilosophie school of philosophy, which sought a unity in nature to prove that a Weltseele, a world spirit or force, was the sole power in place in nature.

Naturphilosophie strongly influenced the Danish scientist Hans Christian Ørsted while he was doing his graduate studies in Germany. When he returned to Denmark, Ørsted embraced this belief in the unity of forces and sought demonstrable evidence of a link between electricity and magnetism. In 1813, he published results of an experiment that demonstrated that an electrical current moving through a wire deflected a compass needle.

A few years later, during the early 1820’s, French scientist André-Marie Ampère found that a circular coil of wire carrying a current acted like a magnet and that current moving in parallel wires caused an attraction or repulsion depending on the direction of the current in the wires. Ampère’s work showed that electricity and magnetism were clearly related.

These experimental results intrigued two members of London’s Royal Institution, Humphry Davy , its director, and his assistant, Michael Faraday, who repeated and extended Ørsted’s work in 1820 and 1821. The Royal Institution had been founded in 1799 to spread scientific knowledge and conduct scientific experiments. It was thus befitting for Faraday to conduct a series of experiments treating electromagnetism, and he published a compendium of existing knowledge about the field in his “Historical Sketch of Electromagnetism” in late 1821 and early 1822. This review of the subject heightened Faraday’s interest in seeking a unity of nature’s forces.

In his search for unity, Faraday brought a theoretical construct shaped by Naturphilosophie and his theological beliefs grounded in the small fundamentalist sect known as the Sandemanians. His religious beliefs instilled in him the notion that nature derived from a single force: God. As he investigated nature, he sought an economy to, and unity of, nature that endorsed those beliefs. During the 1820’s, he conducted experiments to confirm the relationships among electricity, heat, light, and magnetism.

At the Royal Institution, Faraday had a basement laboratory in which he investigated many developing scientific concepts. There, in 1821, he demonstrated that a bar magnet rotated around a wire carrying a current and postulated that circular lines of force accounted for the path of that motion. These results, producing electromagnetic rotation, set in place a continuing effort by Faraday over many years to use experimental methods to discover the connections between electricity and magnetism. In doing so, he held steadfast to the principle that sound scientific theories must rely on strong experimental evidence. Faraday constantly revised his theories through experiment with a superb talent that combined preceptual, conceptual, and laboratory-based information to generate new knowledge. He recorded his laboratory investigations meticulously in a diary he kept over a forty-year period. It is a rich source of information about his speculations in the world of science and his ingenuity in explaining theories with elegant and carefully planned public demonstrations and lectures.

A skilled experimentalist, Faraday continually addressed the issue of electromagnetism during the 1820’s. By 1824, he believed that a magnet should act on an electrical current, just as Ørsted had demonstrated that an electrical current acted on a magnet. With Faraday’s many duties at the Royal Institution, where he became director of the laboratory in 1825, and his private work as a consulting scientist, he turned to the issue repeatedly but sporadically for years. Finally, in 1831, he began a series of experiments, which continued from August to November, in which he focused on electromagnetic induction.

During those four months, Faraday conducted 135 experiments to test his hypothesis that electricity could be induced by magnetic substances. His first success came in late August, when he arranged two separate coils of wire, insulated from each other, around opposite sides of an iron ring and suspended a magnetic needle over this ring. He then introduced a current in one wire coil and detected an induced current in the second wire coil on the ring—the magnetic needle oscillated. This experimental evidence confirmed his long-held belief that electricity was related to magnetism: The movement of electrical current in a coil of wire produced a current in another coil when these two coils were linked by a magnetic material.

Although Faraday’s experiment confirmed most of his expectations, it also had one surprising result. Faraday had assumed that the induced current in the second coil would be continuous; instead, he discovered that it was transient—he obtained a pulse of current, not a continuous flow. However, the evidence of his August, 1831, experiment convinced him that electromagnetic induction was a fact, and this led him to conduct several more tests over the next few months building on the evidence of his first researches. By mid-October of 1831, he was producing an electric current directly from a magnet itself by the reciprocal motion of a magnet in and out of a cylindrical helix.

The key to this process lay in Faraday’s strong belief in a field composed of lines of force: Continuous electricity was produced only when a conductor was moved through a magnetic field cutting the lines of force. An experiment conducted in late October, 1831, confirmed this: Faraday rotated a copper disc between the poles of a powerful electromagnet and obtained a continuous current. These results provided him with the experimental evidence he needed to prove his theory of the unity of forces between electricity and magnetism. On November 24, 1831, he presented those findings to the Royal Society in a series of lectures titled Experimental Researches in Electricity. In this public setting, Faraday demonstrated the reciprocal linkage between magnetism and electricity.

Significance

With this brilliant experimental work, Faraday established the scientific principles that resulted in the development of electric generators, or dynamos. These devices became the foundation of a new electrical technology using generators and motors as a new power source in the latter half of the nineteenth century. His work also reinforced the unity principles of Naturphilosophie and convinced many nineteenth century physicists that electricity, magnetism, and light were interrelated. Further, Faraday’s experimental evidence provided a foundation for James Clerk Maxwell, a distinguished British physicist, to analyze electromagnetic forces propagated through space. Maxwell’s resulting equations became the basis for field theory and provided unifying mathematical statements for the observations of electromagnetic forces studied by experimentalists such as Ørsted and Faraday.

Faraday’s work represents the importance of careful, thorough experimentation in nineteenth century physics. Although Faraday held strong convictions about the nature of forces, he tested those notions in the laboratory and constantly revised his interpretations of events based on his experimental results. The Royal Institution, his scientific and personal home for almost forty years, provided the framework and facilities for his ongoing research. His special skill in devising definitive experiments allowed him to discover electromagnetic induction and to explain it to the scientific community in elegant ways. In doing so, he was a founder of the scientific world of field theory and the technological world of electrical power.

Bibliography

Agassi, Joseph. Faraday as Natural Philosopher. Chicago: University of Chicago Press, 1971. Agassi portrays Faraday as an adventuresome thinker rather than an experimental genius.

Cantor, Geoffrey. Michael Faraday: Sandemanian and Scientist: A Study of Science and Religion in the Nineteenth Century. New York: St. Martin’s Press, 1991. Cantor provides a thorough analysis of Faraday’s scientific work emphasizing the linkages between that work and Faraday’s Sandemanian religion.

Gooding, David, and Frank A. J. L. James, eds. Faraday Rediscovered: Essays on the Life and Work of Michael Faraday, 1791-1867. New York: Macmillan, 1985. Several contemporary Faraday scholars provide new insights into Faraday’s methods and achievements.

Hamilton, James. A Life of Discovery: Michael Faraday, Giant of the Scientific Revolution. New York: Random House, 2002. Biography focusing on Faraday’s life, including his relationships with friends and colleagues, and less on his scientific discoveries.

Mahon, Basil. The Man Who Changed Everything: The Life of James Clerk Maxwell. Chichester, England: Wiley, 2003. Sympathetic biography of the physicist who extended Faraday’s work that explains Maxwell’s scientific work.

Thomas, John Meurig. Michael Faraday and the Royal Institution: The Genius of Man and Place. Bristol, England: Institute for Physics, 1997. Description of Faraday’s life, work, and legacy by the director of Great Britain’s Royal Institution. Well illustrated and easy for nonscientists to understand.

Williams, L. Pearce. Michael Faraday: A Biography. New York: Basic Books, 1965. This thorough biography by a noted historian of science places Faraday and his achievements within the context of nineteenth century science.

‗‗‗‗‗‗‗. The Origins of Field Theory. New York: Random House, 1966. This cogent treatment of field theory provides a context for understanding Faraday’s work within the larger framework of nineteenth century field physics.