dielectric polarization

Dielectric polarization is the slight separation of positive and negative electric charges within an insulator, or dielectric, when it's exposed to an external electric field. This occurs because the electric field distorts the electron clouds around atomic nuclei, making one side of the atom slightly positive and the other slightly negative. In some materials, like water, molecules that are already polarized can rotate to align with the electric field.1

This polarization reduces the electric field within the dielectric material. The amount of polarization is measured by the electric dipole moment, which is the distance between the separated charges multiplied by the magnitude of one of the charges. Polarization (P) is defined as the electric dipole moment (p) per unit volume (V) of the material: P = p/V. Dielectrics are important in capacitors, as they can increase capacitance and reduce the voltage between electrodes.213