ABSTRACT
This chapter examines the characteristic superfluid properties of superconductors, as phenomena. The successful description of superconductors was the two-fluid model, developed by C. J. Gorter and H. B. G. Casimir in the 1930s. According to the two-fluid model, a superconductor behaves as though it contains electrons of two different types, the normal electrons, which behave at least approximately like electrons in normal metals, and the superelectrons, which have striking and unusual properties. Magnetic fields and the magnetic vector potential play a large role in the physics of superconductors and we need to be clear about our handling of them. The property of superconductivity can be exceedingly useful, most obviously, perhaps, in building powerful electromagnets which absorb no power and in making microprocessor elements which dissipate no heat but it can also be helpful to the low-temperature experimentalist.
