Question

Point charges $q_1$ and $q_2$ are placed in air at a distance 'r'. The ratio of the force on charge $q_1$ by charge $q_2$ and force on charge $q_2$ by charge $q_1$ is?

• A. $\frac{q_1}{q_2}$
• B. $\frac{q_2}{q_1}$
• C. $1$
• D. ${\left(\frac{q_1}{q_2}\right)}^2$

Answer 1

Answer: (C)

$1$

Force on charge $q_1$ by $q_2$ is given by $F_{12}=\frac{1}{4\pi {ϵ}_o}\frac{q_1{q}_2}{r^2}$
Force on charge $q_2$ by $q_1$ is given by $F_{21}=\frac{1}{4\pi {ϵ}_o}\frac{q_2{q}_1}{r^2}$
Thus ratio of force $\frac{F_{12}}{F_{21}}=1$