Question

Two insulated charged metallic spheres $P$ and $Q$ have their centres separated by a distance of $60cm$. The radii of $P$ and $Q$ are negligible compared to the distance of separation. The mutual force of electrostatic repulsion if the charge on each is $3.2\times {10}^{-7}C$ is:

• A. $5.2\times {10}^{-4}N$
• B. $2.56\times {10}^{-3}N$
• C. $1.5\times {10}^{-3}N$
• D. $3.5\times {10}^{-4}N$

Answer 1

Answer: (B)

$2.56\times {10}^{-3}N$

Here
$q_1=q_2=3.2\times {10}^{-7}C,r=60cm=0.6m$
Electrostatic force,
$F=\frac{1}{4\pi {\epsilon }_0}\frac{q_1{q}_2}{r^2}=\frac{9\times {10}^{-3}{(3.2\times {10}^{-3})}^2}{{\left(0.6\right)}^2}=2.56\times {10}^{-3}N$