1. The problem statement, all variables and given/known data An electric dipole of moment p is placed at a distance r from a point charge +q. The angle between p and r is phi. Show that the energy of interaction between the dipole and the charge is -pqcos(phi)/4[tex]\pi[/tex][tex]\epsilon[/tex]0r^2 Derive equations for a)a radial force on the dipole b)a force on the dipole normal to r c)a couple on the dipole 2. Relevant equations 3. The attempt at a solution I have proved the first part of the question using the integral of the torque between [tex]\phi[/tex]0 and [tex]\varphi[/tex] and setting [tex]\varphi[/tex]0 to 90degrees and I believe that questions a, b and c are simple manipulations of the proved equation, but no book I read will give me a proof or an explanation of the 'radial force' and how to prove questions a, b and c could anyone help?