Effects of varying magnetic
fields
The merger of electricity and
magnetism from distinct phenomena into electromagnetism is tied to three
closely related events. The first was Hans Christian Ørsted's accidental
discovery of the influence of an electric current on a magnetic
needle--namely, that magnetic fields are produced by electric currents.
Ørsted's 1820 report of his observation spurred an intense effort by
scientists to prove that magnetic fields can induce currents. The second
event was Faraday's experimental proof that a changing magnetic field can
induce a current in a circuit. The third was Maxwell's prediction that a
changing electric field has an associated magnetic field. The technological
revolution attributed to the development of electric power and radio
communications can be traced to these three landmarks.
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