Magnetism

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Electrical resistance of certain materials, known as superconductors, changes abruptly from a non- zero value to zero as their temperature is lowered below a critical temperature Tc (0). An interesting property of superconductors is that their critical temperature becomes smaller than Tc(0), if they are placed in a magnetic field, that is, the critical temperature Tc(B) is a function of the magnetic field strength B. The dependence of Tc(B) on B is shown in the figure.