Two charges each equal to $\eta q\left({\eta }^{-1}<\sqrt{3}\right)$ are placed at the corners of an equilateral triangle of side a. The electric field at the third corner is E₃

$\begin{array}{l}{E}_1=\frac{\eta q}{4\pi {\epsilon }_0{a}^2},E_2=\frac{\eta q}{4\pi {\epsilon }_0{a}^2}\\ \text{ Therefore }\overrightarrow{E_3}={\overrightarrow{E}}_1+{\overrightarrow{E}}_2\\ \Rightarrow E_3=\sqrt{E_1^2+E_2^2+2E_1{E}_2\cos {60}^{\circ }}=\frac{\sqrt{3}\eta q}{4\pi {\epsilon }_0{a}^2}\\ \text{ Since }{\eta }^{-1}<\sqrt{3}\\ \Rightarrow 1<\sqrt{3}\eta \\ \Rightarrow \sqrt{3}\eta >1\\ \Rightarrow \frac{\sqrt{3}\eta q}{4\pi {\epsilon }_0{a}^2}>\frac{q}{4\pi {\epsilon }_0{a}^2}\\ \Rightarrow E_3>E_0 \left(here E_0=\frac{q}{4\pi {\epsilon }_0{a}^2}\right)\end{array}$