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On this day 29 Aug) in 1831, Michael Faraday discovered the induction of one current by another in his famous induction ring experiment. This is one of the few really great experiments in the history of science and familiar to every student of #physics
In his experiment, Faraday wrapped two wires (copper) around opposite sides of an iron ring. 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. He plugged one wire into a galvanometer, and watched it as he connected the other wire to a battery. He saw a transient current, which he called a "wave of electricity", when he connected the wire to the battery. Then he was astonished to see the galvanometer needle jump in the opposite direction when he disconnected the wire to the battery.
He discovered this induction was due to the change in magnetic flux that occurred when the battery was connected and disconnected. He explained this induction, using a concept he called line of force. However, scientists at the time widely rejected his theoretical ideas, mainly because they were not formulated mathematically. An exception was JamesClerkMaxwell, who used Faraday's ideas as the basis of his quantitative electromagnetic theory.