- #1
MrMuscle
- 12
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Attempt:
Bound charge density refers to the electric charge that is bound to the atoms or molecules within a material. It is not free to move and is therefore not affected by external electric fields.
Free charge density refers to the electric charge that is free to move and is affected by external electric fields. Bound charge density, on the other hand, is not free to move and is only affected by internal electric fields within a material.
An expression for bound charge densities can be found by using the concept of polarization, which is the separation of positive and negative charges within a material. This can be represented mathematically using the polarization vector P, which is related to the bound charge density by the equation ρ_b = -∇ · P.
David J. Griffiths is a physicist and author of the textbook "Introduction to Electrodynamics" which is commonly used in studying electromagnetism. In this textbook, he provides a thorough explanation of polarization and its relation to bound charge densities, making it a valuable resource for finding an expression for bound charge densities.
The expression for bound charge densities in Griffiths is based on the assumption that the material is linear and isotropic, meaning that its properties do not change with direction. In reality, most materials are not perfectly linear and isotropic, so this expression may not be accurate in all cases.