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Useful Identities for Electrodynamics




\begin{multicols*}{2}\setlength{\columnseprule}{0.5pt}
\bigskip
\par
\centerl...
...}{r^2\sin^(\theta)} \ppartialdiv{f}{\phi} \end{displaymath}\par
\end{multicols*}

Integration by Parts (examples)



\begin{displaymath}\divg{(f\vA)} = f(\divg{\vA}) + (\vA \cdot \grad)f \end{displaymath}


\begin{displaymath}\int_{V/S} \divg{(f\vA)}dV = \int_{V/S} f(\divg{\vA}) + \int_{V/S}
(\vA \cdot \grad)f \end{displaymath}


\begin{displaymath}\oint_S (f\vA)\cdot d\va = \int_{V/S} f(\divg{\vA}) + \int_{V/S}
(\vA \cdot \grad)f \quad\textrm{(divergence theorem)}\end{displaymath}


\begin{displaymath}\int_{V/S} f(\divg{\vA}) = \oint_S (f\vA)\cdot d\va - \int_{V/S}
(\vA \cdot \grad)f \quad\textrm{(integration by parts, or:)}\end{displaymath}


\begin{displaymath}\int_{V/S} (\vA \cdot \grad)f = \oint_S (f\vA)\cdot d\va - \int_{V/S}
f(\divg{\vA}) \quad\textrm{(integration by parts)}\end{displaymath}



\begin{displaymath}\curl{(f\vA)} = f(\curl{\vA}) - (\vA \times \grad)f \end{displaymath}


\begin{displaymath}\int_{S/C} \curl{(f\vA)}\cdot d\va = \int_{S/C} f(\curl{\vA})\cdot
d\va - \int_{S/C} (\vA \times \grad)f \cdot d\va \end{displaymath}


\begin{displaymath}\oint_C f\vA \cdot d\vell = \int_{S/C} f(\curl{\vA})\cdot
d\v...
... (\vA \times \grad)f \cdot d\va \quad\textrm{(Stokes'
theorem)}\end{displaymath}


\begin{displaymath}\int_{S/C} f(\curl{\vA})\cdot d\va = \oint_C f\vA \cdot d\vel...
... \times \grad)f \cdot d\va \quad\textrm{(integration by
parts)}\end{displaymath}





Robert G. Brown 2014-08-25