Collection of videos and photos of a superconductor
A heavy magnet placed defies gravity and experiences levitation when placed on a bulk superconductor. This is due to the characteristic Meissner Effect experienced by superconductors. Usually when two magnets approach they either attract (N and S poles) or repel each other (N-N or S-S). However, this phenomenon does not occur in superconductors as the magnetic field can be completely removed. Therefore, the magnetization always occurs towards the direction where the magnetic fields cancel each other, producing a repulsive force.
The Meissner Effect itself does not realize stable levitation in superconductors. Another important characteristic to consider is the Pinning Effect, where a quantum magnetic flux partially becomes trapped inside the superconductor, pinning its position, and thus stabilizing the levitation between the superconductor and the magnet.
As long as the relative magnetic field distribution of the superconductor and the magnet are not varied during superconducting magnetic levitation, they are able to move freely. As seen in (1) the levitation of the permanent magnet and (2) the levitation of the large magnet, demonstrates the reason why the floating magnetic disc remains in position, being able to rotate due to the constant magnetic field distribution of the magnet.
A large resistance between the superconductor and the magnet exists. A large force is required to modify the magnetic field distribution, and hence change the relative height and position of the magnet above the superconductor.
(1) Levitation of a 15cm diameter permanent magnet The movie shows a strong magnet experiencing levitation when placed on a bulk superconductor that is cryogenically cooled.
(2) Levitation of a large magnet Let's further see the large-scale application of magnetic levitation. Approximately 100 bulk superconductors are cryogenically cooled and a disc woven with strong magnets is placed on top. The disc levitates even though its weight is approximately 60kg. Moreover, the disc remains levitated even when a person stands on the disc. There is no change in levitation height with loads of up to maximum 300kg.
Superconductors have further interesting characteristics as demonstrated by the following video. A bulk superconductor is immersed in a liquid nitrogen filled container placed on a wooden stage, under which there is a globe. A strong magnet attached to the globe suspends the globe in mid-air when the beaker is removed. This phenomenon occurs because the bulk superconductor is hanging the magnet above the globe and is called Fishing Effect.
Fishing (Hanging) experiment
(4) Application of Levitation Experiment
We have demonstrated these superconducting characteristics using a miniature "Superconducting Rollercoaster". The inside of the car is made up of a number of Yttrium-based superconducting wires, which is made to levitate and run on a railroad composed of strong magnets.
The individual characteristics of the rollercoaster are difficult to see because of the speed of operation, however let's examine the "superconducting vehicle" by taking out a single rail. The Fishing Effect is demonstrated when the railroad is inclined and inverted. The car remains suspended above the rail and does not fall.
This miniature rollercoaster has a spring mechanism at the end of its travel. The spring mechanism forces the vehicle back, but as the railroad is set at an incline the car again moves towards to the spring mechanism. This oscillatory motion continues until the superconducting wires warm up and lose their superconductivity.
The photo shows the levitation height between the rail and the carriage.
(5) "SF Train" in the Wonderland in Superconductivity.