## Faraday’s Experiments in Electricity and Magnetism Michael and Sarah Faraday had no children, but he was an active uncle with his nieces and nephews often playing in his laboratory. They later remembered his reactions to successes and failures and their descriptions of an excited uncle contrasted with his always sober lab notebook recording of his results By the time Faraday was working on his own, he knew all of chemistry. Davy had been a pioneer and was devoted to an atomistic-molecular view which rubbed off on Faraday who tended to think in terms of particulate matter all of his working life. His skills as an analytic chemist were second to none and he was in considerable demand for industrial consultation, fitting right into the goals of the Royal Institution. He created compounds of chlorine (discovered by Davy) and carbon, he isolated Benzine (and other organic molecules), liquefied chlorine, and discovered paramagnetism. He made important advances in alloying of steel. He was the go-to man in Britain for industrial chemistry innovation. Our concern is with this research into electricity and magnetism. Let’s consider each of his major discoveries in their historical order. ### The Motor Oersted’s results in 1820 electrified the Davy-Faraday laboratory. Their lab was proficient in electro-chemistry and so they must have had many of the materials required in order to repeat Oersted’s experiment, and they did in great detail. It was Faraday who imagined that Oersted’s compass demonstrating a circular relationship around a current-carrying wire might imply that magnets might themselves feel circular force around a wire. He had the clever idea to construct such a device, making use of the fact that mercury is a good conductor of electricity, while still being a fluid.
Look at the left side of the figure above. The beaker of mercury has a bar magnet attached on a swivel at the bottom and at the top of the pool of liquid, a wire just breaks the surface. The wire running off the bottom to the left is attached to a battery and the vertical wire (ignoring the right hand part of the picture) is attached to the other terminal of the battery. When current flows through the mercury and the wire, the magnet swivels around its base in a circle around the upper wire. That's a different demonstration of what Oersted observed -- that a magnetic disturbance surrounds a current. Here the magnet swinging around the wire is experiencing that disturbance. The right hand picture shows is sort of the opposite. The magnet is fixed and has its own magnetic disturbance and the current-carrying wire is free to swivel...mechanical motion is induced in the current, where before mechanical motion is induced in the magnet. In each case (left and right) the circuit is completed through the mercury and the vertical wires. Faraday connected the two experiments together as a show-and-tell stunt demonstrating the complimentary aspects of the same phenomenon: electrical energy is converted into mechanical motion, which is...the first motor. When you flip the switch on a wall and your garage door goes up, that's a motor at work. The opposite of a motor is a generator, in which you convert mechanical energy into electrical energy. Your car has a generator that takes the mechanical energy of the engine and converts it into electrical energy to charge your battery.

Electrical energy can induce circular mechanical motion in a circuit.

Faraday knew that this was a significant discovery. In his notebook he wrote, “Very satisfactory, but make a more sensible apparatus.” But his 14 year old brother-in-law, who was in the lab with Faraday’s wife, Sarah noted later that they all danced around the apparatus and then went to the circus to celebrate. (He even prepared small hand-held versions of the Faraday Motor that he gave to colleagues for their amusement.) Faraday had none of the “Newton upbringing” and so his mind created different pictures. This idea of circular forces didn’t fit into a Newtonian force-world and in this regard, Faraday was completely on his own. In 1821, young Faraday was asked to write an article which would summarize the all of the known electrical and magnetic phenomena. By this point, he was an extraordinarily careful experimenter and exceedingly clever with his notebooks, inventing an indexing system that he’d use his entire career. Instead of just reviewing the literature, he decided to repeat all of the experiments that had ever been done on electricity which for a genius like Faraday, led him into new territory. ```{admonition} Please answer Question 2 for points: :class: danger Generator or Motor? ``` ### His Day Job By 1825 Faraday was the director of the Royal Institute and inherited fund raising and financial affairs which were a considerable burden, as the place was nearly broke. Its purpose was originally to assist British industry with solutions which could be sold or which would increase efficiency in the nation’s factories. That contrasted with Faraday’s own personal desire to continue to do fundamental research, undirected by practical application. He found time to do so, but it was less than he would have liked. It was not until 1831—the year that Davy died—that he was able to return to basic research in electricity and magnetism. But he was always working on matters of public good and industrial progress. Basic research was inserted when he had time. But one thing he had time for was pay-back. Remember his good fortune in life had come with an opportunity of a chance public lecture. Faraday devoted himself, throughout his life, as an engaging and entertaining presenter of science to the public. As director, he instituted a nearly weekly series on Fridays—always exactly one hour—and he created a Christmas series for children. The Royal Institution Christmas Lectures have been given every year (except during WWII) from a virtual “who’s who” of British scientists. Look at that overflow crowd in one of his last lectures below. Michael Faraday was the world’s first “Mr Wizard.”