Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: cold magnets and superconductivity

Learn more physics!

Most recent answer: 02/22/2011
Q:
Hi mike, i have a few questions and it seems you know what your talking about with magnets, superconducters and tempurature. Although alittle seperate from your original topic, I am wondering if a Neodymium magnet would become less effective at supercooled tempurature, using liquid nitrogen and/or liquid helium ... and if Niobium tin (Which will work around 4.2Kelen)/Noibium titianium would work as a superconducting magnet cooled by Liquid Nitrogen (77K) in conjunction with liquid helium (2.17K)... if you need me to refraze this i can.
- Brennan (age 20)
Hayward, CA, USA
A:
Brennan- If this doesn't quite get to what you're asking, try a follow-up.

Those neodynium magnets should work fine when they're cold. Don't cool them too quickly, since I worry that they might break under thermal strain. So far as I know, they won't crack if the temperature only changes slowly.

Niobium/tin does make a good superconducting wire. (see ) However, you still need to use liquid helium to get it cold enough to superconduct. One uses liquid nitrogen  to initially cool down the dewar that the liquid helium will go in, since  helium has a low latent heat of vaporization and is expensive- it costs way too much to directly use it for the first cool-down. In some dewars, there's a liquid nitrogen outer shield as well.

Mike W.

(published on 02/22/2011)

Follow-up on this answer.