CHAPTER 1 - Conducting and Insulating Materials

Abstract

This chapter focuses on conducting and insulating materials. If a material allows an electric current to flow through it easily, it is known as a conductor, and if it effectively prevents the flow of current, it is known as an insulator. If for instance two rods of the same size were made, one from a typical conducting material and the other from a typical insulating one, the ratio of the ability to conduct electricity would be of the order of 1020. It will be seen that the nucleus can contain one or several positive particles or protons and similarly that the number of electrons can be one or more. There is a maximum number of electrons that will remain in any one shell and hence, when one shell is full, another at a greater radius is started. In metals, the outer shells have not a full complement of electrons and also the atoms are closely packed together so that electrons can wander from atom to atom readily. Changes in temperature imply changes in the energy of the electrons in the atoms of a substance and, as the mobility of these electrons governs the ease with which the electricity can be conveyed, it is natural that temperature and conduction should be interrelated. The property of opposing conduction is known as the resistivity of a material, symbol p, and the reciprocal 1/p is known as the conductance.