![]() Theory Faraday's law of induction and Lenz's law Lenz's law gives the direction of the induced emf and current resulting from electromagnetic induction. In 1834 Heinrich Lenz formulated the law named after him to describe the "flux through the circuit". Heaviside's version (see Maxwell–Faraday equation below) is the form recognized today in the group of equations known as Maxwell's equations. In Maxwell's model, the time varying aspect of electromagnetic induction is expressed as a differential equation, which Oliver Heaviside referred to as Faraday's law even though it is slightly different from Faraday's original formulation and does not describe motional emf. An exception was James Clerk Maxwell, who used Faraday's ideas as the basis of his quantitative electromagnetic theory. ![]() However, scientists at the time widely rejected his theoretical ideas, mainly because they were not formulated mathematically. įaraday explained electromagnetic induction using a concept he called lines of force. For example, he saw transient currents when he quickly slid a bar magnet in and out of a coil of wires, and he generated a steady ( DC) current by rotating a copper disk near the bar magnet with a sliding electrical lead (" Faraday's disk"). ![]() Within two months, Faraday found several other manifestations of electromagnetic induction. This induction was due to the change in magnetic flux that occurred when the battery was connected and disconnected. He saw a transient current, which he called a "wave of electricity", when he connected the wire to the battery and another when he disconnected it. He plugged one wire into a galvanometer, and watched it as he connected the other wire to a battery. Based on his understanding of electromagnets, he expected that, when current started to flow in one wire, a sort of wave would travel through the ring and cause some electrical effect on the opposite side. In Faraday's first experimental demonstration (August 29, 1831), he wrapped two wires around opposite sides of an iron ring or " torus" (an arrangement similar to a modern toroidal transformer). It was discovered independently by Joseph Henry in 1832. Įlectromagnetic induction was discovered by Michael Faraday, published in 1831. Change in the magnetic flux of the left coil induces a current in the right coil. A diagram of Faraday's iron ring apparatus. But when the small coil is moved in or out of the large coil (B), the magnetic flux through the large coil changes, inducing a current which is detected by the galvanometer (G). ![]() When the coils are stationary, no current is induced. History Faraday's experiment showing induction between coils of wire: The liquid battery (right) provides a current that flows through the small coil (A), creating a magnetic field. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License. Use the information below to generate a citation. Then you must include on every digital page view the following attribution: If you are redistributing all or part of this book in a digital format, Then you must include on every physical page the following attribution: If you are redistributing all or part of this book in a print format, Want to cite, share, or modify this book? This book uses the
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