Electromagnetic properties of HTS

The behaviour of magnetic fields in superconductors is quite different in many ways from that in normal metals. It is however simpler and more intuitively obvious than in iron magnetic circuits. There is a close parallel with the pinning of domain walls in ferromagnets and the induction of eddy currents in copper. The connection with the latter is that copper exerts a viscous force on flux, while a superconductor exerts a frictional force. Perhaps the most important concept is the Bean model. This takes the critical current density as a measurable property and determines a wide range of properties from it. Most problems can be thought of either in terms of magnetic flux or induced currents and it is helpful to use both concepts.