electromagnetic induction

By moving a magnet in and out of a coil of wire, Faraday found it possible to create an AC voltage across the wires in the direction he moved the magnet. This is the principle that explains why your house now receives an AC voltage from the power company.

Electromagnetic induction results in a temporary change in the external magnetic field. An interaction occurs between the induced field (formed when the current is induced in the conductor) and the inducing field.

This proved to Faraday that it was possible to produce an electric current by the movement of magnetic flux relative to a coil of wire.

Electromagnetic Induction is the principle used in electric generators (also called alternators), microphones, electric guitars, transformers,and Tesla coils.

There are in fact a few ways of using induction to do this; the Japanese-built maglev system uses this basic repelling principle. The magnetic fields generated are of the same pole, resulting in a repelling force. In contrast, the German system uses a design where the train 'grips' a track, and the underside of the grips generates the magnetic field. In this case, the fields generated are of opposite poles, and the resulting attraction lifts the bottom of the grips up towards the rail; this lifts the train up.

The Japanese system is simpler to build and run; however, it results in a rougher ride and thus slower speeds, since the separation distance is only regulated in one direction. In addition, the open shape of the track's active surface makes it easy for foreign objects to interfere with and possibly damage the train.

The German system results in a smoother, more tightly-regulated ride, but requires much more complex and fast-acting computer control to reamin within the feedback loop, since the tolerances for this much smaller vertical separation are much much tighter.