1. The problem statement, all variables and given/known data Show that the energy of an ideal dipole p in an electric field E is given by U = -p ⋅ E 2. Relevant equations Work = θτ where τ is torque τ = p × E 3. The attempt at a solution U = ∫(p × E) dθ' (from θ to 0, since the dipole will eventually align itself with the magnetic field.) =∫pE(sinθ')dθ' =-pE(cosθ') with limits θ to 0 =-pE + pE(cosθ) =p ⋅ E - pE That's not what I needed to prove. Help?