In 1820, the Danish physicist Hans Christian Ørsted was delivering a lecture when he noticed that the needle of a compass reacted when an electric current from a battery was switched on and off. Ørsted became the first person to publish the discovery that when electricity flows through a wire, it produces a magnetic field. Although other scientists experimented with Ørsted’s discovery of the relationship between electricity and magnetism, it was not until the 1830s that Michael Faraday, the son of an English blacksmith, proved that Ørsted’s discovery worked in reverse: that when a magnetic
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