The superconductivity below the critical temperature has been observed to disappear
in the presence of an applied magnetic field exceeding a critical value denoted by Bc.
Thi s critical field depends on the temperature and i s a characteristic of the material .
Figure 8.47 shows the dependence of the critical field on the temperature. The critical field i s maximum, £c(0), when T = 0 K (obtained by extrapolation8). As long as
the applied field i s below Bc at that temperature, the material i s in the superconducting state, but when the field exceeds Bc, the material reverts to the normal state. We
know that in the superconducting state, the applied magnetic field lines are expelled
from the sample and the phenomenon i s called the Meissner effect. The external
field, in fact, does penetrate the sample from the surface into the bulk, but the magnitude of thi s penetrating field decreases exponentially from the surface. If the field
at the surface of the sample i s B0, then at a distance x from the surface, the field i s
The superconductivity below the critical temperature has been observed to disappearin the presence of an applied magnetic field exceeding a critical value denoted by Bc.Thi s critical field depends on the temperature and i s a characteristic of the material .Figure 8.47 shows the dependence of the critical field on the temperature. The critical field i s maximum, £c(0), when T = 0 K (obtained by extrapolation8). As long asthe applied field i s below Bc at that temperature, the material i s in the superconducting state, but when the field exceeds Bc, the material reverts to the normal state. Weknow that in the superconducting state, the applied magnetic field lines are expelledfrom the sample and the phenomenon i s called the Meissner effect. The externalfield, in fact, does penetrate the sample from the surface into the bulk, but the magnitude of thi s penetrating field decreases exponentially from the surface. If the fieldat the surface of the sample i s B0, then at a distance x from the surface, the field i s
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