dielectrics in an electric field behave according to their internal structure.They are also called non-conductors, as is known, they are substances which do not substantially conducting electricity.They do not contain free charge carriers which would be capable of moving inside this dielectric.
molecule - is the smallest particle of a substance that retains its chemical properties.It, in turn, itself consists of atoms with the positively charged nucleus and negatively charged electrons.The molecules are generally neutral.As the theory of covalent bonds are formed in one or more pairs of electrons, atoms become common for connecting, ensure the stability of the molecules.
For each of the types of charges - positive (nuclei) and negative (electrons) - there is a point, which, as it is their "center of gravity" (electric).These points are called the poles of the molecule.In the case that in the molecule electrical centers of gravity of opposite charges: positive and negative - it will be a non-polar (not having a dipole moment).
structure of the molecule can be asymmetrical, for example, there can be two dissimilar atoms, then to some extent offset the total to happen a pair of electrons in the direction of one of the atoms.Clearly, in this case, the uneven distribution of opposite charges (positive and negative) within the molecule will result in a mismatch of electrical centers of gravity.The resulting molecule is called the polar or have a dipole moment.
main property of dielectrics is their ability to polarize.
dielectrics are polarized in an electric field.This means that their atoms, the electrons begin to move along elongated orbits.As a result, some of the surface is negatively charged, the other - positively.Thus, an electric field in the dielectric which respectively called internal.That is, at the same time dielectrics the electric field (external and internal), which at the same time in opposite directions.
resultant electric field has a voltage equal to the voltage difference of the larger and smaller fields.It should be noted that the field strength in the insulator, regardless of its type, is always smaller than the external electric field, which caused its polarization.
polarization intensity is directly proportional to the dielectric constant of the dielectric.The smaller it is, the less intense in the dielectric polarization occurs and the stronger the electric field in it.
charges appear not only on the surface but also at the ends of the insulator, but their transition upon contact with the electrode is impossible, because the insulator is attracted to the electrode by Coulomb forces.
dielectrics in an electric field, if it is strong, and it is possible to increase the tension, for certain values of the tension begin to break, that is, the atoms will rip electrons.This will lead to the ionization process of dielectrics, whereby they become conductors.
magnitude of the external field, which leads to the breakdown of the dielectric, it is called the breakdown voltage.A corresponding limit voltage at which the dielectric breaks - breakdown voltage.We know another name for ultimate stress - dielectric strength.
It should be noted that only the dielectric in an electric field has the internal field, which generally disappears when the shooting outside.
