Meissner Effect

When cooled below its critical temperature using liquid nitrogen, a superconductor expels magnetic fields and becomes a perfect diamagnet. This phenomenon, known as the Meissner effect, allows a magnet to levitate above the superconductor until it warms above its transition temperature.

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

Superconductor Meissner effect - pl4nb33:

Meissner Effect - Physlab.org:

📄 Meissner or Flux pinning? - Quantum Levitation. Explains difference between Meissner effect and Flux pinning. https://quantumlevitation.com/meissner-or-flux-pinning/?utm_source=sciencedemos&utm_medium=referral&utm_campaign=edu-directories

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

• 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.

• 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).

• 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.)