ELECTRO-MAGNETIC INDUCTION

The link between electricity and magnetism was discovered in 1824 by Oested, who found that current in a wire could move a magnetic compass needle.  A few years later the opposite effect was discovered.  A magnetic field in motion forces electrons to move, producing current.  This important effect was studied by the English physicist and pioneer in electromagnetism, Michael Faraday (1791 – 1867); the American physicist, H. F. E. Lenz (1804 – 1865).

The Henry unit of inductance is named after Joseph Henry.  The farad unit of capacitance is named after Michael Faraday, who did important work in electrostatics as ell as electromagnetism.  There is no unit named after Lenz, but Lenz law explains many important electromagnetic effects with a varying electric current.

Electromagnetism combines the effect of an electric current and magnetism.  Electrons in motion, or any current, always have an associated magnetic field.  For the opposite effect, when a magnetic field is in motion, the work put into this action forces electrons to move in any conductor within the field, producing current.  These electromagnetic effects have many practical applications that are the basis for motors and generators ; More fundamentally these effects explain why a coil of wire has special characteristics in a circuit when the current is changing in value.

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