Polarization, bound charge and electric displacement
Macroscopic electric polarization P gives bound volume charge ρ_b=−∇·P and surface charge σ_b=P·n at a material boundary.
Key knowledge
Macroscopic electric polarization P gives bound volume charge ρ_b=−∇·P and surface charge σ_b=P·n at a material boundary. D=ε₀E+P satisfies ∇·D=ρ_free. In a local linear isotropic dielectric, P=ε₀χ_eE and D=εE, with ε=ε₀(1+χ_e).
Values and equations
ρ_b=−∇·P; σ_b=P·n; D=ε₀E+P; ε=ε₀(1+χ_e)
- P,D
- Polarization and electric displacement C m⁻²
- ρ_b,ρ_free
- Bound/free volume charge density C m⁻³
- σ_b
- Bound surface charge density C m⁻²
- E
- Electric field V m⁻¹
- ε,ε₀
- Absolute/vacuum permittivity F m⁻¹
- χ_e,n
- Susceptibility and outward unit normal
Conditions and scope
- Macroscopic averaging; for the displayed σ_b=P·n formula, n points outward from the polarized body and the exterior polarization is zero. Between two polarized media use n·(P₁−P₂) with n from 1 to 2. χ_e here is scalar for local linear isotropic response.
- Anisotropy, frequency dependence, spatial dispersion and nonlinear response require more general constitutive laws.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Classical Electromagnetism (2014): Polarization: Equations 496–507: volume divergence, D, free-charge law and local linear susceptibility. Source ε is relative and is converted here to absolute ε=ε₀(1+χ_e). The surface charge is derived by integrating −∇·P across the piecewise field discontinuity, not claimed to be a displayed formula on this page.
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Entry details
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- physics-polarization-displacement
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- university-core.1
- Structured reference record
- University core expansion