No Resistance—No Magnetic Field

Abstract

Superconductors intrigue us because they do many wondrous things, but they especially intrigue us because they do one thing perfectly: conduct electricity. Few things in nature exhibit true perfection but superconductors carry current with absolutely no resistance. Although, as we have seen, no measurement technique can distinguish between zero and some very small number, we have strong reason to believe that the resistance in a superconductor really is zero. This simple departure from ordinary electrical behavior is what makes superconductors truly super. But what constitutes ordinary electrical behavior?