Physics - Elecrostatics Question with Solution | TestHub

Considering two dipoles with charges $2q \& q$, we can write the equivalent setup as shown below:

Therefore, net dipole moment is $P_{net}=6ql$ in the leftward direction.

Potential required, 

$$\begin{gathered} V=\frac{K\overrightarrow{p}·\overrightarrow{r}}{r^3} \\ =\frac{9\times {10}^9\left(6q\mathcal{l}\right)}{r^2}\cos \left({120}^{\mathrm{o}}\right) \end{gathered}$$

$=-\left(27\right)\left(\frac{q\mathcal{l}}{r^2}\right)\times {10}^9$

Therefore, $\alpha =27$.