Tag: magnetically levitated trains

How can currents and electromagnets encounter frictional effects without touchin…

Lou Bloomfield Leave a comment

How can currents and electromagnets encounter frictional effects without touching?

When you slide a strong magnet quickly above a metal surface, there is a friction-like magnetic drag effect. This effect occurs even when the two objects don’t touch. The origin of this effect lies in the repulsions between the metal and magnet: it’s strongest slightly in front of the moving magnet so the magnet encounters some difficulty heading forward. The reason why the magnetization of the metal is strongest slightly in front of the moving magnet is related to the loss of energy by current moving in the metal. The magnetization (of the metal surface) in front of the moving magnet is fresher than the magnetization behind it. The current responsible for the magnetization behind the magnet has been flowing for long enough to have lost energy. But the faster you move the magnet across the metal surface, the less time the currents in it have to lose energy and the less friction-like force the magnet experiences.

How does a magnet induce a metal to become attracted to the magnet? Does the met…

Lou Bloomfield Leave a comment

How does a magnet induce a metal to become attracted to the magnet? Does the metal become a magnet also?

A steady, motionless magnet can’t induce a piece of normal metal (not iron, cobalt, or nickel) to become magnetic. Only a moving or changing magnet can do that. When a metal is exposed to a changing or moving magnet, it does become magnetic. That metal becomes a type of magnet; an electromagnet. The metal itself isn’t really the magnet; the electric charges inside it are. These charges move in response to the changing or moving magnet nearby and they become magnetic, too. The effect is always repulsive, not attractive. The temporarily magnetic metal repels the magnet that is making it magnetic.

How does running current through a coil cause a magnetic field?

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How does running current through a coil cause a magnetic field?

Electricity and magnetism are interrelated in a great many ways. At the very basic levels, they are manifestations of the same fundamental physical concepts. As a result, electricity can produce magnetism and magnetism can produce electricity. One way in which electricity can produce magnetism is for charged particles to move. When an electric current passes through a coil (or any wire, for that matter), it creates a magnetic field. The coil develops a north magnetic pole and a south magnetic pole. I can’t really explain why because the answer is simply that moving charges create magnetic fields; that’s the way our universe works and no one has ever seen otherwise.

If magnetic trains are to work, wouldn’t friction on the bottom of the train cre…

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If magnetic trains are to work, wouldn’t friction on the bottom of the train create thermal energy which would destroy the magnetism of the train?

When a magnetically levitated train is operating properly, it doesn’t touch the track and experiences no friction. In principle, it shouldn’t get hot at all. The magnetic drag effect will warm the track slightly, but that won’t matter to the train’s magnets. Actually, the train’s magnets will almost certainly be superconducting wire coils with currents flowing in them. That type of magnet doesn’t depend on the magnetic order of permanent magnets. It’s the magnetic order of permanent magnets that is destroyed by heat. An electromagnetic coil will stay magnetic as long as current flows through it, even if it’s so hot that it’s ready to melt.