Dielectrics in the Electric Field скачать в хорошем качестве

Dielectrics in the Electric Field

Dielectrics in the Electric FieldDielectrics are substances that conduct electricity rather poorly. Any non-ionized gases, some liquids, like distilled water, solid substances, like glass and china, are all types of dielectrics.Dielectrics contain virtually no free electrons, and, under standard conditions, the orderly motion of electric charge within such substances is impossible. Depending on the structure of molecules building up the dielectric, there exist two kinds: polar and non-polar dielectrics.The polar dielectrics consist of molecules, in which in the positive and negative charge distribution centers do not coincide. The polar molecules can be roughly viewed as electric dipoles, that is the aggregate of the two opposite point charges that are equal in module and located at a certain distance from each other.Under standard conditions, the dipoles of the dielectric are spread chaotically. If we place a dielectric into an external homogenous electric field, each dipole will be subjected to forces tending to turn the dipole in such a way so that its axis is directed along the flux. In this case, the positively charged particles would shift towards the electric field, whereas their negatively charged counterparts - towards the opposite side.Such shift of the dielectric's positive and negative bound charges towards the opposite directions is called polarization.The non-polar dielectrics contain molecules or atoms, where the positive and negative charge centers coincide. When subjected to an external field the electronic orbit of a molecule suffers deformation. This results in the positive and negative charge centers shifting with respect to each other along the flux in the opposite direction. Meanwhile, the molecules become dipoles.Since the field created by dipoles is directed opposite the external field, the field inside the dielectric becomes weaker. The extent of such weakness depends upon the electric properties typical of the given dielectric. It is characterized by such indicator as a dielectric constant, which describes the electric field strength module inside a homogenous dielectric as opposed to that in vacuum.