Question

Two point charges $-q$ and $+q$ are located at points $(0,0,-a)$ and (0,0,a) respectively. The electric potential at point $(0,0,z)$ is :

• A. $\frac{qa}{4\pi {\epsilon }_0{z}^2}$
• B. $\frac{q}{4\pi {\epsilon }_{0}a}$
• C. $\frac{2qa}{4\pi {\epsilon }_0(z^2-a^2)}$
• D. $\frac{2qa}{4\pi {\epsilon }_0(z^2+a^2)}$

Answer 1

The correct option is C $\frac{2qa}{4\pi {\epsilon }_0(z^2-a^2)}$

The potential is given by,
$P=kq/(z-a)-kq/(z+a)=2kqa/(z^2-a^2)$