======Meissner Effect======


<WRAP right box>
**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
\\
**Categories:** {{$demo.categories}}
\\


**Alternative titles:** Magnetic Field Expulsion, Floating Magnet
</WRAP>

====Summary====                   
{{$demo.summary}}



====Procedure====  
  - Place a sample of yttrium-barium-copper-oxide (YBCO) superconductor in a container.  
  - Pour liquid nitrogen over the sample until it is fully cooled below its critical temperature.  
  - Hold a small permanent magnet above the superconductor.  
  - Observe the magnet levitate as the superconductor expels the magnetic field.  
  - Allow the liquid nitrogen to evaporate; when the superconductor warms, the magnet will gradually lose levitation and fall.



====Links==== 
Superconductor Meissner effect - pl4nb33: 
{{youtube>JIjzJKnpahA?}}\\

Meissner Effect - Physlab.org: 
{{youtube>M2xIlaZ5zQM?}}\\



📄 Meissner Effect - PhysLab: [[https://physlab.org/class-demo/meissner-effect/]]\\


====Variations====
  * Use different shapes or sizes of magnets to see how the levitation changes.  
  * Demonstrate flux pinning by slightly displacing the magnet and observing how it locks into position.  
  * Compare the effect using different superconducting materials.



====Safety Precautions====
  * Wear cryogenic gloves and face protection when handling liquid nitrogen.  
  * Handle superconductors and magnets with care; avoid direct skin contact with extremely cold surfaces.  
  * Ensure good ventilation to prevent oxygen displacement from evaporating nitrogen.  
  * Do not confine liquid nitrogen in a sealed container (risk of explosion).




====Questions to Consider====
  * Why does a superconductor expel magnetic fields when cooled below its critical temperature? (It becomes a perfect diamagnet due to the Meissner effect.)  
  * What role does temperature play in this demonstration? (Below the critical temperature, the material becomes superconducting; above it, superconductivity is lost.)  
  * How is flux pinning different from simple levitation? (Flux pinning allows the magnet to remain suspended in fixed positions due to trapped magnetic field lines in the superconductor.)  
  * What practical applications arise from the Meissner effect? (Maglev trains, frictionless bearings, superconducting power lines.)