11 - Electrical properties of metals, insulators, and dielectrics

Abstract

This chapter focuses on the electrical properties of materials. These are the properties of concern in electrical power generation and transmission facilities, consumer electronics, and computer and telecommunications equipment. Electrical as well as optical and magnetic properties of materials are concerned with the electronic structure of atoms and the response of electrons to electromagnetic fields. Electrical conductivity distinctions between metals and nonmetals essentially hinge on the nature of the electron distributions in atoms. In ionic and covalent solids only very fixed numbers of electrons are tolerated by atoms; local excesses or deficiencies in their number are resisted. An excess electron flows to an atom with one too few and vice versa; free electrons are very scarce. Electron currents largely counterbalance one another so the net current is vanishingly small. In metals, however, electron numbers about atoms are not so rigidly controlled. Enough free electrons are always available to smooth local depletions and accumulations; electrons fed into a wire at one end will, therefore, be readily removed in equal number at the other end. Metals are the best conductors of electricity and, therefore, have the lowest resistivities. Insulators, comprising ceramics, glasses, and polymers have the highest resistivities. Conduction by ions, not electrons, is often the chief mechanism for charge transport.