|ELECTRICITY AND MAGNETISM - MAGNETIC MATERIALS - TEMPERATURE AND MAGNETISM||Order|
Description: This demonstration includes a high temperature superconducting disk consisting of Yttrium, barium, copper and oxygen. It becomes superconducting below 90 K. The disk is attached to an absorbent material that insulates and holds liquid nitrogen to keep the superconductor cool longer.
A magnetic track is also included. The magnets are arranged so that the magnetic poles are all aligned one way in the front of the track, and in the opposite way in the back of the track. This creates a magnetic field that is generally uniform along the length of the track, but it is not uniform off the sides or up and down.
One more device that is included is a block of magnets with their polarities all alternating. The expulsion of magnetic field from a superconductor is an intrinsic property of any superconductor. Below a certain magnetic field the superconductor expels nearly all magnetic flux by circulating current near its surface. Flux Pinning In some cases the magnetic flux becomes locked or "pinned" inside a superconductor. Flux pinning is desirable in high-temperature ceramic superconductors to prevent flux movements which introduce a resistance and dissipate energy. The pinning is achieved through defects in the crystalline structure of the superconductor usually resulting from grain boundaries or impurities.
Instructions: Cool the superconducting disk for with LN2 for about 30 seconds. Use the tweezers to place the superconducting disk on the magnetic track or on the block of magnets. Hold the superconductor in place for a few seconds until it is securely pinned in the magnetic field.
Careful not to let the disk fall more than a few inches, or it may get damaged.
Setup Time: 15 minutes
Quant. in Demo Room: 1
Source: Quantum Experience ltd
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