Superconductivity and the Meissner Effect.

WWC Physics Photo of the week.  Donald F. Collins

Figure 1.  The YBCO disk (black) and a amall magnet resting on the disk at room temperature.  Photo by Cayce Canfield, physics student at Warren Wilson College.

Figure 2.  The YBCO disk has been chilled with liquid Nitrogen (about 77 deg K).  the magnet levitates a few mm above the superconducting disk.  Superconductors exclude magnetic fields, leading to the levitating forces.  This effect is called the Meissner effect after the name of its discoverer.  The level of liquid nitrogen is at the base of the black disk.  The black disk is supported by a rubber stopper.  Notice the fog fumes from the liquid nitrogen.

Figure 3.  Another view of the levitating magnet.