E _ = − ∇ _ ϕ − 1 c ∂ t A _ {\displaystyle {{\underline {E}}=-}{\underline {\nabla }}\phi -{\color {Gray}{\frac {1}{c}}}{{\partial }_{t}}{\underline {A}}}
E ( r _ ) = α ( q r _ | r _ 3 | ) {\displaystyle E\left({\underline {r}}\right)=\alpha \left(q{\frac {\underline {r}}{\left|{{\underline {r}}^{3}}\right|}}\right)}
mit
α = 1 4 π ε 0 {\displaystyle \alpha ={\frac {1}{4\pi {{\varepsilon }_{0}}}}}