Faraday's motor and induction ring*

In Oct 1820, the Dane, H C Øersted, had discovered that passing electric current through a wire produced a magnetic field – a compass needle was deflected. Michael Faraday reversed the process and created the first motor. Not a practical device but an experiment to show that that a magnet (left hand flask) would rotate around a wire carrying current and, equally that a wire carrying current would rotate round a magnet (right hand flask). In the picture, the vessels are full of mercury thus allowing the current to flow. All modern motors and generators rely on this discovery. Faraday also discovered that when two coils are wound on an iron ring a change in the flow of current in one produces a change in current in the other, this is the basis of the old-fashioned children's electric-shock coil. When a low voltage fed through a coil of a few turns is interrupted, it produces a very high voltage - but a safe low current - in another coil of many turns. This causes nasty but safe shocks. The same principle makes the plugs of a car spark.

This a photograph of Faraday’s original "Inductor" ring. The actual ring can be seen in the basement exhibition at the Royal Institution building.

 

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