ELECTROSTATICS OF CONDUCTORS AND DIELECTRICS

Materials fall into two broad classes for the purposes of electrostatics. Conductors, such as metals, contain a large number of charges (in metals, free electrons not bound to any particular atom) that are free to move throughout the material; when an external field is applied, or when the conductor is charged, these free charges rearrange themselves until the conductor reaches a new state called electrostatic equilibrium, in which several distinctive properties hold (developed in section 1.7.1). Dielectrics, or insulators, by contrast, have no free charges at all -- every electron remains bound to its own atom or molecule -- but an external field can still slightly displace the bound positive and negative charge within each atom or molecule, a phenomenon called polarisa …