Đáp án:
\(\begin{array}{l}
a.\\
F = 40N\\
b.\\
E = 22500000V/m
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
F = k\frac{{|{q_1}{q_2}|}}{{A{B^2}}} = {9.10^9}\frac{{|{{12.10}^{ - 6}}. - {{3.10}^{ - 6}}|}}{{0,{{09}^2}}} = 40N\\
b.\\
{E_1} = \frac{{k|{q_1}|}}{{A{C^2}}} = {9.10^9}\frac{{{{12.10}^{ - 6}}}}{{0,{{12}^2}}} = 7500000V/m\\
{E_2} = \frac{{k|{q_2}|}}{{B{C^2}}} = {9.10^9}\frac{{| - {{3.10}^{ - 6}}|}}{{0,03}} = 30000000V/m\\
E = |{E_1} - {E_2}| = |7500000 + 30000000| = 22500000V/m
\end{array}\)