:<math> \mu = \mu_r \mu_0, \quad \quad </math>
where ε<sub>0</sub> = 8.854e85410×10<sup>-12 </sup> F/m, μ<sub>r</sub> = 1.257e257×10<sup>-6 </sup> H/m, and ε<sub>r</sub> and μ<sub>r</sub> are called relative permittivity and permeability of the material, respectively.
The constitutive parameters relate the field quantities in the material medium: