Magnetic Levitation

Magnetic fields are actively excluded from superconductors (Meissner effect). If a small magnet is brought near a superconductor, it will be repelled becaused induced supercurrents will produce mirror images of each pole. If a small permanent magnet is placed above a superconductor, it can be levitated by this repulsive force. Levitation currents in the superconductor produce effective magnetic poles that repel and support the magnet. The black ceramic material in the illustrations is a sample of the yttrium based superconductor.
By tapping with a sharp instrument, the suspended magnet can be caused to oscillate or rotate. This motion is found to be damped, and will come to rest in a few seconds.



Uses

Maglev transportation

Main article: Maglev

Maglev, or magnetic levitation, is a system of transportation that suspends, guides and propels vehicles, predominantly trains, using magnetic levitation from a very large number of magnets for lift and propulsion. This method has the potential to be faster, quieter and smoother than wheeled mass transit systems. The technology has the potential to exceed 6,400 km/h (4,000 mi/h) if deployed in an evacuated tunnel.^[14] If not deployed in an evacuated tube the power needed for levitation is usually not a particularly large percentage and most of the power needed is used to overcome air drag, as with any other high speed train. Some maglev Hyperloop prototype vehicles are being developed as part of the Hyperloop pod competition in 2015–2016, and are expected to make initial test runs in an evacuated tube later in 2016.

The highest recorded speed of a maglev train is 603 kilometers per hour (374.69 mph), achieved in Japan on April 21, 2015, 28.2 km/h faster than the conventional TGV speed record.

Magnetic bearings

• Magnetic bearings
• Flywheels
• Centrifuges
• Magnetic ring spinning

Levitation melting

Main article: Levitation melting

Electromagnetic levitation (EML), patented by Muck in 1923, is one of the oldest levitation techniques used for containerless experiments.^[17] The technique enables thelevitation of an object using electromagnets. A typical EML coil has reversed winding of upper and lower sections energized by a radio frequency power supply.

History

• 1839 Earnshaw's theorem showed electrostatic levitation cannot be stable; later theorem was extended to magnetostatic levitation by others
• 1912 Emile Bachelet awarded a patent in March 1912 for his “levitating transmitting apparatus” (patent no. 1,020,942) for electromagnetic suspension system
• 1933 Superdiamagnetism Walther Meissner and Robert Ochsenfeld (the Meissner effect)
• 1934 Hermann Kemper “monorail vehicle with no wheels attached.” Reich Patent number 643316
• 1939 Braunbeck’s extension showed that magnetic levitation is possible with diamagnetic materials
• 1939 Bedford, Peer, and Tonks aluminum plate placed on two concentric cylindrical coils shows 6-axis stable levitation.
• 1961 James R. Powell and BNL colleague Gordon Danby electrodynamic levitation using superconducting magnets
• 1970s Spin stabilized magnetic levitation Roy M. Harrigan
• 1974 Magnetic river Eric Laithwaite and others
• 1979 transrapid train carried passengers
• 1981 First single-tether magnetic levitation system exhibited publicly (Tom Shannon,Compass of Love, collection Musee d'Art Moderne de la Ville de Paris)
• 1984 Low speed maglev shuttle in Birmingham Eric Laithwaite and others
• 1997 Diamagnetically levitated live frog Andre Geim
• 1999 Inductrack permanent magnet electrodynamic levitation (General Atomics)
• 2000 The first man-loading HTS maglev test vehicle “Century” in the world was successfully developed in China.
• 2005 homopolar electrodynamic bearing

Benifits

Advantages

• Magnetic levitation trains in Germany and Japan are capable of reaching speeds up to 500 kmh^–1. They are faster than conventional train systems.
• Maglev systems do not use steel wheels on steel rails. Because magnetic levitation trains do not touch the guide way the high cost of maintaining precise alignment of the tracks to avoid excessive vibration and rail deterioration at high speeds is not a problem.
• Maglevs can provide sustained speeds greater than 500 kmh^–1 limited only by the cost of power to overcome wind resistance.
• Maglevs do not touch the guide way. This confers advantages such as: faster acceleration and braking, greater climbing capability; enhanced operation in heavy rain, snow and ice.
• Maglev transportation offers an alternative to mass transit problems in major metropolitan areas where traffic on ground and air has become too congested.
• Maglev systems are energy efficient. For long distance travel they use about half the energy per passenger as a typical commercial aircraft.

Maglev is an electrified transportation system. They reduce the use of petroleum, and pollute the air less than aircraft, diesel locomotives and cars.

In summary, the major appeal of the maglev solution is to provide mass transit that is high speed, environmentally clean and reduced noise when compared to aircraft at airports.

PERSONAL VIEWS In my own views the magnetic levitation is important to the rain ways system