Question 265 of 311

Two point dipoles of dipole moment $\vec{p}_1$ and $\vec{p}_2$ are at a distance $x$ from each other and $\vec{p}_1 || \vec{p}_2$.
The force between the dipoles is :

A$\frac{1}{4 \pi \varepsilon_0} \frac{4 p_1 p_2}{x^4}$B$\frac{1}{4 \pi \varepsilon_0} \frac{3 p_1 p_2}{x^3}$C$\frac{1}{4 \pi \varepsilon_0} \frac{6 p_1 p_2}{x^4}$D$\frac{1}{4 \pi \varepsilon_0} \frac{8 p_1 p_2}{x^4}$

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Answer: (B) $\frac{1}{4 \pi \varepsilon_0} \frac{3 p_1 p_2}{x^3}$

Force of interaction
$\mathrm{F}=\frac{1}{4 \pi \epsilon_0} \cdot \frac{3 \mathrm{p}_1 \mathrm{p}_2}{\mathrm{r}^4}$