Physics - W.E.P. Question with Solution | TestHub

At the distance of closest approach, the entire $\mathrm{KE}$ of a particle is converted into electric potential energy. i.e.. $\mathrm{KE}=\mathrm{PE}$ Here, KE of the particle = work done in moving the particle in uniform electric field (E) through a distance (D) $$=qE\times D$$ PE of the particle = potential $\times$ charge $$=\frac{q}{4\pi c_0{\gamma }_0}\times Q$$ $\therefore qED=\frac{qQ}{4\pi {\epsilon }_0{\gamma }_0}\Rightarrow r_0=\frac{Q}{4\pi {\epsilon }_{0}ED}$