To determine the force exerted on a test charge $q_2$ at position $\textbf{r}_2$, we can utilize Cuolomb’s law: $$\textbf{F}_2 = \frac{q_1 q_2}{4\pi\varepsilon_0} \frac{\textbf{r}_2 - \textbf{r}_1}{\lvert\textbf{r}_2 - \textbf{r}_1\rvert^3}, \tag{1}$$ for a charge $q_1$ placed at the position $\textbf{r}_1$. $\varepsilon_0$ is called vacuum permittivity and takes the value: $\varepsilon_0 = 8.8542 \,\! \times \,\! 10^{-12}\, \text{C}^{2}\,\text{N}^{-1}\text{m}^{-2}$.