Polarization density refers to the measure of the extent to which the electric charges within a material are displaced from their equilibrium positions. It is a property of electrical materials that describes the formation of electric dipoles within the material when subjected to an external electric field.

When an electric field is applied to a material, the positive and negative charges within the material experience a force that causes them to shift slightly from their original positions. This displacement of charges results in the creation of electric dipoles, where positive and negative charges are separated by a small distance.

The polarization density (P) is defined as the dipole moment per unit volume of the material. It represents the overall dipole moment per unit volume induced in the material by the applied electric field. Mathematically, polarization density is given by:

P = Σ(pi) / V

where P is the polarization density, Σ(pi) is the sum of the dipole moments of all the dipoles within the material, and V is the volume of the material.

In simpler terms, polarization density describes how much the charges within a material shift in response to an electric field, leading to the creation of electric dipoles. It is an important concept in understanding the behavior of electrical materials and their response to external electric fields.