Superconductivity

Introduction

The fascinating phenomenon of superconductivity and its potential applications have attracted the attention of scientists, engineers and businessmen. Intense research has taken place to discover new superconductors, to understand the physics that underlies the properties of superconductors, and to develop new applications for these materials. In this unit you will read about the history of superconductors, taking a brief look at their properties. You will also learn about modelling the properties of superconductors and the two different types of superconductor that exist today.

Superconducting electromagnets produce the large magnetic fields required in the world's largest particle accelerators, in MRI machines used for diagnostic imaging of the human body, in magnetically levitated trains (Figure 8) and in superconducting magnetic energy storage systems. But at the other extreme superconductors are used in SQUID (superconducting quantum interference device) magnetometers, which can measure the tiny magnetic fields (~10^−13T) associated with electrical activity in the brain, and there is great interest in their potential as extremely fast switches for a new generation of very powerful computers.

In this unit we will focus on the macroscopic electrodynamic properties of superconductors, and particularly on some of the properties that can be explained in terms of electromagnetism concepts with which you should be familiar. A full understanding of superconductivity requires knowledge of materials science and quantum theory, and discussion of these aspects is beyond the scope of this unit. We begin with a review of some of the main developments over the last hundred years, then describe in more detail some of the key electromagnetic properties. These can be modelled in a simple way without using quantum mechanics, and we shall show how this can be done. Finally, we distinguish between the type of superconductivity shown by most of the elemental superconductors, known as type-I superconductivity, and that shown by superconducting alloys that have commercial applications, known as type-II superconductivity.

This unit is an adapted extract from the Open University course Electromagnetism (SMT359) [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]