EM Theory Math Tricks

This is a short overview of useful mathematical relationships and concepts in EM theory

Divergence Theorem

Kronecker delta

Very useful gradient relation

$$\frac{\vec{r}-{\vec{r}}^{\prime }}{|\vec{r}-{\vec{r}}^{{}^{prime}}|}=-\nabla$$

DELTA FUNCTION The divergence of this is 0 for all values where x $\ne$ 0 $\infty$ for x=0

$$\frac{dF}{dx}=0$$

because the slope has no slope Aka Derivative of step function