What is polarization P in a dielectric?

What is polarization P in a dielectric?

• A. P is the dipole moment per unit volume
• B. P is the electric field
• C. P is the potential
• D. P is the charge density

Answer: (A)

Polarization describes how a dielectric becomes polarized under an electric field: it is the dipole moment per unit volume inside the material. Each molecule or atom develops a tiny separation of positive and negative charges, and the sum of these dipole moments, divided by the material’s volume, gives the polarization vector P. Its direction corresponds to the average orientation of the dipoles, and its magnitude relates to how strongly the material responds to the field. This quantity has units of coulombs per square meter and leads to bound charges inside the material, with a bound volume charge density of -∇·P and a bound surface charge density of P·n. In linear dielectrics, P is proportional to the electric field: P = ε0 χ_e E, and the displacement field is D = ε0 E + P. The electric field is a different field that describes forces on charges, the potential is a scalar whose gradient gives the field, and the charge density ρ describes how much free or bound charge is present, not how much dipole moment per volume exists.

Polarization describes how a dielectric becomes polarized under an electric field: it is the dipole moment per unit volume inside the material. Each molecule or atom develops a tiny separation of positive and negative charges, and the sum of these dipole moments, divided by the material’s volume, gives the polarization vector P. Its direction corresponds to the average orientation of the dipoles, and its magnitude relates to how strongly the material responds to the field. This quantity has units of coulombs per square meter and leads to bound charges inside the material, with a bound volume charge density of -∇·P and a bound surface charge density of P·n. In linear dielectrics, P is proportional to the electric field: P = ε0 χ_e E, and the displacement field is D = ε0 E + P. The electric field is a different field that describes forces on charges, the potential is a scalar whose gradient gives the field, and the charge density ρ describes how much free or bound charge is present, not how much dipole moment per volume exists.