A8.2 The Meissner Effect
If a conductor is placed in a magnetic field, the interaction of the magnetic field with the circulation of electrons in the surface of the conductor sets up its own “mirror-image” magnetic field. This field opposes the external magnetic field and as a result the applied magnetic field is “expelled”.
In the diagrams below B represents the applied magnetic field, T is the temperature and
TC\textsf{T}_\textsf C
is the critical temperature for that metal.
Figure 8.1 Normal conductor
Normal conductor: the magnetic field lines are affected by the current in the conductor.
Figure 8.2 Superconductor
Superconductor: the magnetic field lines are expelled by the current in the conductor.
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