What's a superconductor?

Superconductors have two outstanding features:

  1. Zero electrical resistivity. This means that an electrical current in a superconducting ring continues indefinitely until a force is applied to oppose the current.
  2. The magnetic field inside a bulk sample is zero (the Meissner effect). When a magnetic field is applied current flows in the outer skin of the material leading to an induced magnetic field that exactly opposes the applied field. The material is strongly diamagnetic as a result. In this experiment, a magnet floats above the surface of the superconductor

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