Question

A charge $q_1$ exerts a force of $45N$ on a charge of $q_2={10}^{-5}C$ located at a point $0.2m$ from $q_1$. The magnitude of $q_1$ is

• A. $4\times {10}^{-8}C$
• B. $2\times {10}^{-5}C$
• C. $3\times {10}^{-6}C$
• D. $5\times {10}^{-8}C$

Answer 1

The correct option is B $2\times {10}^{-5}C$

As we know electrostatic force between two charges $F=\frac{k{q}_1{q}_2}{r^2}$

$\Rightarrow 45=\frac{(9\times {10}^9)\left(q_1\right)\left({10}^{-5}\right)}{(0\cdot 2{)}^2}$

$\Rightarrow q_1=\frac{45\times 0\cdot 2\times 0\cdot 2}{9\times {10}^9\times {10}^{-5}}$

$\Rightarrow q_1=2\times {10}^{-5}C$