The smallest electric force between two charges placed at a distance of 2m is $(x+0.76){10}^{-29}$ N. Find value of $x$. $\left(\frac{1}{4\pi {\epsilon }_0}=9\times {10}^9\text{ SI unit }\right)$

$F=\frac{1}{4\pi {\in }_0}\frac{q_1{q}_2}{r^2}$

For F to be smallest

$q_1,q_2$ must be smallest

$i.e{\text{ q}}_1=q_2=1.6\times {10}^{-9}C$

$F_{\min }=\frac{9\times {10}^9\times 1.6\times 1.6\times {10}^{-38}}{4}=9\times 0.64\times {10}^{-29}$

$F=5.76\times {10}^{-29}N$

$F=(5+0.76){10}^{-29}N\Rightarrow x=5$