Superconductors that possibly work at room temp.

Anonymous Coward writes "University of Houston, Texas researchers have found subtle signs of superconductivity in nanotubes of carbon. They may conduct electricity without any resistance, at temperatures stretching up past the boiling point of water. See the story on EurekAlert"

Comments

Close, but not quite.

[caffeinated_bunsen]

All conductors oppose changes in magnetic fields by having currents induced which try to preserve the original magnetic flux through the conductor. If there was no magnetic field, and you turn one on, a current will be induced so as to oppose the field. In a non-superconductor, those currents don't flow for very long before ohmic resistance does its thing. In a superconductor, they flow until the external magnetic field is removed, and the original flux is achieved without an induced current.

Persistent currents, on the other hand, are created when you cool a superconducting ring (doesn't work with solid chunks because of the Meissner effect) below its critital temperature in a magnetic field, and then remove the external field. The superconductor has to maintain whatever magnetic flux through the ring that was present when it became superconducting, so a current is induced that mimics the external field. That current stays around until either the original external magnetic field is restored or the material ceases to be superconducting.

And I'd damn well better know what I'm talking about, since this will be on the final in 2 weeks.

(I didn't bother with much detail about the Meissner effect and its consequences. If you're confused about the persistent current part, I can explain that in detail.)