Electric potential due to dielectric dipole on equational line at distance r from the centre of the dipole is (P = dipole moment) (assume dipole as very short).
Answer & explanation
Correct answer: option 4
$\text{The potential due to dipole is given by} V = \frac{Pcos\theta}{4\pi\epsilon_0 r^2} $
$\text{ At equatorial point } \theta = 90^o$
$\Rightarrow V = 0$