Dielectric
Dielectric, or insulator, substance that is a poor conductor of electricity and that will sustain the force of an electric field passing through it. This property is not exhibited by conducting substances. Two oppositely charged bodies placed on either side of a piece of glass (a dielectric) will attract each other, but if a sheet of copper is instead interposed between the two bodies, the charge will be conducted by the copper. In most instances the properties of a dielectric are caused by the polarization of the substance. When the dielectric is placed in an electric field, the electrons and protons of its constituent atoms reorient themselves, and in some cases molecules become similarly polarized. As a result of this polarization, the dielectric is under stress, and it stores energy that becomes available when the electric field is removed. The polarization of a dielectric resembles the polarization that takes place when a piece of iron is magnetized. As in the case of a magnet, a