A point charge of magnitude $+3\mu \text{C}$ is placed at the origin. Calculate the electric potential at a point $P$ located $12\text{cm}$ from the charge. Take the potential to be zero at infinity. Use $k=9\times 10^9{\text{N m}}^2{\text{C}}^{-2}$.

Step-by-step solution

1. Convert the distance to metres: $r=12\text{cm}=0.12\text{m}$.
2. Write the expression for potential due to a point charge: $V=\frac{kq}{r}$.
3. Substitute $k=9\times 10^9$, $q=3\times 10^{-6}\text{C}$ and $r=0.12\text{m}$: $V=\frac{9\times 10^9\times 3\times 10^{-6}}{0.12}$.
4. Evaluate the numerator: $9\times 10^9\times 3\times 10^{-6}=2.7\times 10^4$.
5. Divide by $0.12$: $V=\frac{2.7\times 10^4}{0.12}=2.25\times 10^5$ V. Wait, check calculation: $2.7\times 10^4/0.12=2.25\times 10^5$ V. However the correct value is $2.25\times 10^5$ V. (Typo in answer line corrected).

Concept tested: Potential of a point charge

Published 13 September 2026 · How this solution was prepared and checked