Electric susceptibility

Electric susceptibility is a dimensionless measure of how readily a material polarizes in response to an applied electric field. In a linear isotropic dielectric, it relates polarization to electric field through the material’s permittivity.

Electric polarization: Electric polarization is the electric dipole moment per unit volume of a material. Susceptibility quantifies how this dipole density changes when an electric field is applied.
Electric field: An electric field is a vector field describing the electric force per unit charge at each point. Susceptibility describes a material’s response to this applied field.
Capacitance: Capacitance measures the charge stored per voltage difference by a conductor arrangement. A dielectric’s susceptibility affects the capacitance when it fills the space between conductors.
Magnetic susceptibility: Magnetic susceptibility measures how a material’s magnetization responds to an applied magnetic field. It is the magnetic analogue, involving magnetization rather than electric polarization.
Electric permittivity: Electric permittivity describes how an electric field relates to electric displacement in a medium. In a linear dielectric, susceptibility determines permittivity through the relation εᵣ = 1 + χₑ.
Electric dipole moment: An electric dipole moment measures the separation and magnitude of positive and negative charge. Aligned dipole moments within matter produce the polarization measured by susceptibility.
Dielectric spectroscopy: Dielectric spectroscopy measures a material’s frequency-dependent response to an applied electric field. It extracts susceptibility across frequencies to reveal polarization mechanisms and relaxation.
Nonlinear optics: Nonlinear optics studies optical responses that are not proportional to the applied electromagnetic field. In nonlinear regimes, polarization cannot be described by a single constant susceptibility.
Dielectric response: Dielectric response is the change in a material’s polarization and electric properties under an electric field. Susceptibility is a compact measure of one part of this broader response.
Electric displacement field: The electric displacement field accounts for free charge and material polarization in macroscopic electromagnetism. Its relation to the electric field provides another route to define dielectric susceptibility.

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