Problem 3.46

A dipole with an electric moment $\mathbf{p}$ is located at a distance $r$ from a long thread charged uniformly with a linear density $\lambda$. Find the force F acting on the dipole if the vector $\mathbf{p}$ is oriented (a) along the thread; (b) along the radius vector $\mathbf{r}$ (c) at right angles to the thread and the radius vector $\mathrm{r}$.