= Conductive contribution to complex permittivity
{title2=$\varepsilon_{r,\rm eff}=\varepsilon_r+i\sigma/(\omega\varepsilon_0)$}
With phasor convention $e^{-i\omega t}$, the <Ampere-Maxwell law> in a scalar conductor reads $\nabla\times\mathbf H=(\sigma-i\omega\varepsilon_0\varepsilon_r)\mathbf E$. Factoring $-i\omega\varepsilon_0$ gives the displayed effective relative <complex permittivity>. Its positive imaginary conductive term expresses loss in this convention; the sign reverses for $e^{+i\omega t}$. This combines conduction and displacement currents for the same field and must not be confused with the material's loss-free relative permittivity alone.
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