Div D, div E. What rho is it. (electrostatics)

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The discussion centers on the relationship between the electric displacement field (D), electric field (E), and charge densities in isotropic, linear, and homogeneous dielectrics. It clarifies that Maxwell's equation ##\vec \nabla \cdot \vec D = \rho## refers specifically to free charge density, excluding bound charges. The participants confirm that in such dielectrics, the equation ##\vec D = \varepsilon_0 \vec E - \vec P## holds true, leading to the conclusion that bound charges do exist, as indicated by the divergence of polarization (P) not being zero.

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fluidistic
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I know that the D field has to do with free charges. So when we write Maxwell's equation ##\vec \nabla \cdot \vec D = \rho## we mean rho as the free charge density which does not include the bound charges also known as polarized charges.
I know that the E field has to do with both the free charges and bound charges. However if the region I'm concerned about is an isotropic, linear and homogeneous dielectric then ##\vec D = \varepsilon \vec E## and thus ##\vec \nabla \cdot \vec E = \frac{\rho }{\varepsilon }##.
Where rho in this case is also the free charge density.
But I'd have thought that ##\vec \nabla \cdot \vec E = \frac{\rho _\text{free}+ \rho _{\text{bound}}}{\varepsilon }##. I'm guessing this equation is not false, but it's just that the nature of the dielectric makes that ##\vec \nabla \cdot \vec P=0## (which is also worth ##-\rho _\text{bound}##). So that means that in an isotropic, linear and homogeneous dielectric there are no bound charges?
 
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atyy said:
If I understand your notation, I think it is wrong. One should have ε0 in the RHS denominator, like Eq 2 of http://www.pa.msu.edu/~duxbury/courses/phy481/Fall2009/Lecture27.pdf.


Yes you are right, I've just rederived it via ##\vec D = \varepsilon _0 \vec E - \vec P##, taking the divergence.
Therefore I'm left to see that ##\frac{\rho _\text{free}+ \rho _{\text{bound}}}{\varepsilon _0 } = \frac{\rho _\text{free}}{\varepsilon}##.
I can already answer a question in my first post, namely "So that means that in an isotropic, linear and homogeneous dielectric there are no bound charges?", the answer is no, because div P is not worth 0.
 

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