Discussion Overview
The discussion centers on the calculation of the electric displacement field D(r) in a polarized object, specifically whether to account for the electric field created by the polarized object itself or only the external electric field that induced the polarization. The scope includes theoretical aspects of electromagnetism and the relationship between electric fields and polarization in materials.
Discussion Character
- Technical explanation
- Debate/contested
Main Points Raised
- Ray questions whether to include the electric field created by the polarized object when calculating D(r) using the equation D(r) = epsilon E + P.
- One participant asserts that the total electric field must include the field due to the object itself.
- Another participant corrects Ray's equation and provides two equations for D, explaining the distinction between the permittivity in free space and that in the material.
- A participant notes that the electric field inside the object differs from the external electric field that would exist without the object.
- Ray later states that he only needed to include the external field that created the polarization, suggesting a resolution to his initial confusion.
- Another participant agrees that the electric field is the same in both equations presented.
Areas of Agreement / Disagreement
There are competing views regarding the necessity of including the electric field created by the polarized object in the calculation of D(r). While some participants clarify the equations and their implications, Ray concludes that only the external field is necessary for his calculations.
Contextual Notes
There are unresolved aspects regarding the definitions of permittivity and the conditions under which the equations apply, as well as the assumptions made about the electric field in different contexts.