A dipole is placed in an electric field whose direction is fixed but whose magnitude varies with distance it is possible that the dipole experiences 

$\overrightarrow{\tau }=\overrightarrow{p}\times \overrightarrow{E} and F =p\frac{dE}{dr}$. If the field lines are parallel and the dipole axis is perpendicular to the field ,then it experiences a torque but no force if $\frac{dE}{dr}=0 perpendicular to the direction of electric field .$