ABSTRACT
The main objective of this chapter is to give an overview of superconductivity which includes a description of the basic observations of the phenomenon and an indication of the principal applications. We discuss the emergence of superconductivity in certain materials and how these materials are used in four main groups of applications: superconducting solenoids, superconducting magnetometers (SQUIDs), superconducting logic devices and superconducting power electronics devices. Both flux pinning by a superconductor and the Meissner effect are explained, together with the differences between Type i and Type ii superconductors. The onset of superconductivity is discussed as a discontinuous reduction in conductivity to a state with zero dc resistance. It is shown that the resistanceless state is insufficient to explain the Meissner effect in which magnetic flux is completely excluded from the bulk of a superconducting material. Conditions for establishing the presence of superconductivity are given.
