Electromagnetic induction is (also) one of the methods of supporting and propelling a 'maglev
' train. Maglev (Magnetic Levitation
) is achieved by having the track composed of conducting coils. A powerful magnetic field, generated by the train's systems, induces an opposite magnetic field in the track's coil
s, and the interaction between the two keeps the train suspended above the track.
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.