Question

Potential energy of $2$ charges $10nC$ each separated by a distance of $0.09m$ in air is :

• A. $10\mu J$
• B. $1mJ$
• C. $10mJ$
• D. $10J$

Answer 1

The correct option is A $10\mu J$

Magnitude of each charge $q=10nC={10}^{-8}C$

Distance between the charges $r=0.09m$

Potential energy of the charges $U=\frac{k{q}^2}{r}$ where $k=9\times {10}^9$

$\therefore$ $U=\frac{9\times {10}^9\times ({10}^{-8}{)}^2}{0.09}={10}^{-5}J$

$⟹$ $U=10\mu J$