ABSTRACT
It is important to recall that ρν; the electric charge density (C/m2) and J the electric current density (A/m2) are sources that can induce electromagnetic fields or be induced by the fields .
Fundamentally, we can say that materials are composed of charged particles, which are displaced by the applied fields, which in turn modify the propagation of these fields . To describe this at the microscale (unit: atom, molecule, etc .), we need to define the polarizabilities, or equivalently, a scattering parameter, such as a scattering cross section, which will be introduced later . At the macroscale (i .e ., bulk material), we introduce the constitutive parameters we see above:
ε: dielectric permittivity, a measure of how well a material can store energy imposed by an electric field; it is indirectly associated with capacitance .
