Two electric dipoles each of dipole moment p = 6.2 x 10-3 C cm are placed with their axis along the same line and their centres at a distance d = 10-8 m. What is force of attraction between dipoles?

Field at +q due to first dipole = 14πε02pd+l3Force on +q due to first dipole = 14πε02pqd+l3Force on -q due to first dipole = 14πε02pqd-l3Force of interaction = 2pq4πε01d-l3-1d+l3=3p22ε0πd4=201 x 10-16 N ∵d>>l