Maglev Trains

If you've ever tried to push two refrigerator magnets together north-to-north or south-to-south (or faced off against Magneto), you know that magnetic fields can create considerable amounts of force. When mankind isn't harnessing that force to do very scientifically important things like levitating frogs, it can be harnessed to help overcome one of nature's most annoying forces: friction.

The two major energy losses in large trains come from friction—some from the train pushing through air (which isn't going anywhere anytime soon), and some from the steel wheels rolling on the steel track. If we were able to make a floating train, all of that friction from the wheels would be eliminated.

Well, we could. And we did.

(Sorry, should have mentioned you may have wanted to turn down the volume on your headphones there. Moving at almost half the speed of sound tends to be noisy.)

These maglev trains—short for magnetic levitation—use the same forces that tack your little sister's art to the refrigerator to hurl passengers along special tracks, reaching speeds that the Little Engine That Could just can't. No matter how hard he believes in himself.

A typical maglev system uses two sets of magnets: one to levitate the train, and another to propel the floating train down the track.¹³ Rather than permanent magnets (think fridge), the train's magnets are electromagnets, coils of wire that create strong magnetic fields when current flows through them—Ampère's Law in action. This field is attracted to iron guide rails, and the electromagnets are strong enough to create a force that completely offsets the force of gravity, levitating the train anywhere from a few millimeters to several centimeters above the track. Two points science.

But a levitating locomotive, while cool, isn't particularly useful if it isn't, you know, locomotory. In order to move the train, a second set of electromagnets are embedded in the side walls of the track. These alternate orientation, so that the fields seen by the train follow a north-south-north-south pattern down the track. The train itself has two electromagnets in its own side walls, and the north end of the train is pulled towards the south end of the wall magnets at the same time the south end of the train is pushed away by the previous south wall magnet.

This push-pull action occurs all the way along the track, each small bit of magnet accelerating the train until it reaches the high speeds maglev trains are famous for.