Cool a YBCO puck in liquid nitrogen and place on top of magnetic track. The YBCO puck will repel the magnetic fields of the track and levitate. You can also use the Delrin train with the YBCO pucks already fastened to the inside bottom of train. In this case, ensure there is a spacer between the train and the track during cooling. The train with lid (racecar!) helps to insulate keeping the YBCO pucks cooler longer.
Notes: At low enough temperatures, some materials exhibit superconductivity, a phenomenon in which electric currents flow without any resistance. Once a substance becomes a superconductor, it repels all changes in external magnetic fields.
The superconductor levitates by being repelled or field-trapped by the fields of the North-South-North magnetic configuration of the track. The superconductor used in this demonstration is YBa2CuO7 and superconducts at 93 Kelvin. Liquid nitrogen at 77 kelvin is used to achieve this low temperature.
The train we made used superconductors purchased from a company called Superconductive Components, Inc. (You can find them on the web.) We bought hexagonal pucks (0.8 inch face to face, 1/4 inch thick) of the high-temperature superconductor YBCO from them as our levitators. They cost $75 each. This company also makes other levitators for demonstration purposes.
The magnets we used for the track are Neodynium-Iron-Boron magnets. They are some of the strongest magnets in existence, and hence the key to making a really good levitator. We got the ones we used from a small magnet wholesaler from Colorado that we found on the web. (www.wondermagnet.com) The quantity and dimensions of the magnets will be up to you, and will depend on the geometry of your planned demonstration. We used 3 concentric rings of magnets - arranged in North - South - North configuration, mounted on a sheet of magnetic steel. The total cost of the magnets worked out to be about $700 CDN for this demo. Track dimensions: 126cm x 64cm x 15cm.
10:30-11:30am, 2:00-2:30pm Outreach MP125A