Question

The electrostatic potential energy of two point charges, $1$ $\mu$C each, placed $1$ meter apart in air is?

• A. $9\times {10}^3$J
• B. $9\times {10}^9$J
• C. $9\times {10}^{-3}$J
• D. $9\times {10}^{-3}$eV

Answer 1

The correct option is C $9\times {10}^{-3}$J

$\text{Step 1: Formula of Potential energy}$

Electrostatic potential energy is given by $U$ between two charges placed at a separtion $r$ is given by

$\Rightarrow U=\frac{k{q}_1{q}_2}{r}$

$\text{Step 2: Calculations}$

Putting values, $k=9\times {10}^9\frac{N.m^2}{C^2},$

$q_2=q_1=1\mu C=1\times {10}^{-6}C,$

$r=1m$

$\Rightarrow U$$=\frac{9\times {10}^9\times 1\times {10}^{-6}\times 1\times {10}^{-6}}{1}=9\times {10}^{-3}J$

Hence, correct option is $C$.