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Levitating Trains
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Levitating Trains

Credit: Alex Needham
Source: commons.wikimedia.org/wiki/File:A_maglev_train_coming_out,_Pudong_International_Airport,_Shanghai.jpg
License: CC BY-NC 3.0

Maglev trains use magnetic forces to remove the frictional forces between the track and the train. By allowing the train to float on a cushion of air, these levitating trains are able to reach speeds of more than 310 miles per hour.

Amazing But True

Credit: Brandon Fick
Source: http://www.flickr.com/photos/48948205@N00/1817566256
License: CC BY-NC 3.0

Without magnetic forces, Maglev trains would not be able to accelerate over the rail [Figure2]

  • There are two types of magnetic levitation technology:
    1. Electromagnetic suspension: electromagnets inside the train are attracted to a magnetically conductive track.
    2. Electrodynamic suspension: magnetic fields are used to induce currents in metallic conductors.
  • In electromagnetic suspension systems, electromagnets that are attached to the train allow the train to levitate above a steel rail. More unstable than an electrodynamic suspension system, this system's major advantage is that it works at all speeds. Because the magnetic forces vary inversely with the distance cubed, the smallest change in the distance between the track and the electromagnets produces greatly different forces. Therefore, maintaining a precise distance between track and train is the biggest challenge for electromagnetic suspension.
  • In electrodynamics suspension systems (EDS), the train levitates by a combination of attractive and repulsive magnetic forces. The magnetic fields used in an EDS system are created by using either permanent magnets or superconducting magnetics. The major advantage of this system is that the design allows for the correct distance between the train and the track to be held in place by competing attractive and repulsive forces. The biggest drawback, however, is that the system does not work at slow speeds. Because of this, wheels must be used as the system slows down or as the train is accelerating to the point where the magnetic fields can support the weight of the train.
  • Watch Japan's Maglev train in action: 

http://www.youtube.com/watch?v=k_eT4zq8eO0

  • Learn more about Maglev trains below: 

http://www.youtube.com/watch?v=GHtAwQXVsuk

Explore More

Using the information provided above, answer the following questions.

  1. When superconductors are used, why must they be cooled to such cold temperatures?
  2. How do the frictional forces felt by the train change as the speed increases?
  3. What direction do the magnetic field lines flow: north to south or south to north?

Image Attributions

  1. [1]^ Credit: Alex Needham; Source: commons.wikimedia.org/wiki/File:A_maglev_train_coming_out,_Pudong_International_Airport,_Shanghai.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Brandon Fick; Source: http://www.flickr.com/photos/48948205@N00/1817566256; License: CC BY-NC 3.0

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