What's the Use of Bound Charge?

TL;DR

This paper examines the conceptual and practical distinctions between bound charge and actual charge distributions in polarized materials, questioning their equivalence in electrostatic calculations.

Contribution

It clarifies that bound charge is a useful but not fully equivalent representation of charge in polarized materials, especially in dynamic cases.

Findings

Bound charge accurately models electrostatic fields in static polarization.

Bound charge does not fully represent the physical charge distribution in all cases.

The equivalence between bound charge and actual charge is limited to specific conditions.

Abstract

Bound charge is a useful construct for calculating the electrostatic field of polarized material, and it represents a perfectly genuine accumulation of charge. But is such a material in every respect equivalent to a particular configuration of bound charge? The answer is no, and the same goes for bound current and (in the time-dependent case) polarization current.