1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Meissner effect

  1. Jan 14, 2009 #1
    My question is why does the material having no electrical resistance cause it to repell a magnet?

    And how can it repell and attract at the same time? I don't understand how the "flux trapping effect" works.
    I watched this video and it got me really interested in it.
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. Jan 14, 2009 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Here's a simplistic, hand-waving picture.

    Do you know what happens if you try to subject a regular metal to a magnetic field? Have you heard of eddy currents? There's a similar reaction when you try to subject a zero-field cooled SC to a magnetic field. Eddy currents are set up along the surface of the SC which oppose the change in the applied field.

    However, there's a limit to how much magnetic field a SC can push out against. If you exceed this critical field, then it becomes energetically easier for the SC to just turn into a normal material and let the field through. In certain kinds of SC materials (Type II SCs), however, before completely giving up all hope, the SC chooses (for a certain range of fields) an intermediate phase where it lets small portions of itself turn into a normal material and let the field pass through only those regions. This is what leads to flux trapping. The rest of the material is still a SC an still repels the applied field.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook