Question

Electrostatic potential due to charge configuration at a far point P is

• A. $\frac{kqd}{r^2}$
• B. zero
• C. $\frac{kqd}{2r^2}$
• D. $\frac{\sqrt{3}kqd}{2r^2}$

Answer 1

The correct option is C $\frac{kqd}{2r^2}$

Since point P is far it can be treated as point dipole. Therefore,
$V=\frac{K\overrightarrow{p}.\overrightarrow{r}}{r^3}=\frac{kpcos\theta }{r^2}=\frac{kqd}{2r^2}$
As,
$\overrightarrow{p}.\stackrel{\rightharpoonup }{r}=pr\cos \theta$
where, $\cos 60°=\frac{1}{2}$
and $p=qd$.