Bạn tham khảo nhé!
Ta có:
\(\eqalign{
& F = {{k\left| {{q_1}{q_2}} \right|} \over {\varepsilon {r^2}}} \cr
& {q_1} = {q_2} \Rightarrow F = {{k{q^2}} \over {\varepsilon {r^2}}} \cr
& \Rightarrow \left| q \right| = \sqrt {{{F.\varepsilon {r^2}} \over k}} = \sqrt {{{{{9.10}^{ - 3}}{{.2.0,1}^2}} \over {{{9.10}^9}}}} \approx {1,414.10^{ - 7}}C \cr} \)