]> $$\overrightarrow{P}=\overrightarrow{E}\times \overrightarrow{H}\left(\frac{\text{W}}{{\text{m}}^2}\right)$$ $$<P>=\frac{1}{T}\underset{0}{\overset{T}{\int }}p\left(t\right)dt$$ $$<P>=\frac{1}{2}\frac{{E_0}^2}{z_0}$$ $$<P>=\frac{1}{2}\frac{{E_0}^2}{\left|\stackrel{-}{z}\right|}{e}^{-2az}\cos \tau$$ $$<P>=\frac{1}{2}\mathrm{Re}\left\{\stackrel{-}{E}\left(z,t\right){\stackrel{-}{H}}^{\ast }\left(z,t\right)\right\}$$ $$\mathrm{div}\overrightarrow{P}=-\{\sigma E^2+\frac{\partial w_e}{\partial t}+\frac{\partial w_m}{\partial t}\}$$ $$\{\begin{array}{c}{w}_e=\frac{1}{2}{\epsilon }_0{\epsilon }_r{E}^2\\ w_m=\frac{1}{2}{\mu }_0{\mu }_r{H}^2\end{array}$$ $$∯\overrightarrow{P}·d\overrightarrow{A}=-\left(P_{\text{Joule}}+\frac{\partial W_e}{\partial t}+\frac{\partial W_m}{\partial t}\right)$$ $$∯\overrightarrow{P}·d\overrightarrow{A}>0$$ $$∯\overrightarrow{P}·d\overrightarrow{A}<0$$