Question

Explain briefly why the attraction between a point charge and a dipole has a different distance dependence for induced dipoles ($\mathbf{1}\mathbf{/}{\mathbf{r}}^{\mathbf{5}}$ ) than for permanent dipoles ($\mathbf{1}\mathbf{/}{\mathbf{r}}^{\mathbf{3}}$ ). (You need not explain either situation in full detail: just explain why there is this difference in their behavior.)

Short answer

The attraction between a point charge and a dipole has a different distance dependence for induced dipoles ($1/r^5$) than for permanent dipoles ($1/r^3$) due to the difference in the nature of the force exerted by the dipoles.

Step-by-step solution

Attraction between a point charge and different types of dipole

When two opposite charges approach each other, they experience anout of attraction that is given by the Coulomb force, depending on the induced nature of the charge and intensity, the attraction will begin to feel more or less between the charges.

Reasons for different behavior 

In the case of the attraction between a charge and the permanent dipole, the distance dependence is represented as $1/r^3$ , and the attraction between a charge and an induced dipole as $1/r^5$.

In the case of permanent dipoles, the attractive force is shorter than that of induced dipoles because the distortion that occurs due to the point charge is not permanent and happens for a very short period of time. The dipole will find the previous equilibrium, and the attraction will not be there between the permanent dipole and the point charge. But the induced dipole will remain in the same distorted condition as long as the external influence is there.

Thus, the attraction between a point charge and a dipole has a different distance dependence for induced dipoles ($1/r^5$) than for permanent dipoles ($1/r^3$).