In the case of orientation polarization we have material with built _in dipoles that are independent of each other, i.e. they can rotate liberally in sharp distinction with ionic polarization. Here the (generally liquid or gaseous) material should have natural dipoles which can rotate freely. In thermal equilibrium, the dipoles will be arbitrarily oriented and therefore carry no net polarization. The external field aligns these dipoles to some extend and thus induces a polarization of the material. The paradigmatic element is water, that is, H2o in its liquid form.
(A) The prime example is liquid water, where every water molecule is a little dipole that can have any orientation with respect to the other molecule. Moreover, the orientation changes all the time because the molecule moves.
(B) As shown in diagram a bunch of water molecule that from natural dipoles because the negatively charged oxygen and the two positively charge hydrogen atoms have different centres of charge. Every molecule has a dipole moment which can be taken as a vector of constant length. If we only draw a vector denoting the dipole moment, we get in two dimensions a picture like as shown.
(C) When an electric field E is applied tries to align the dipoles parallel to itself as shown. The negative and positive charges experience forces in opposite direction. But they nearly rigid bond between negative and positive charge holds them together, which means that the molecule experiences a torque π about its centre of mass.
(D) This torque π acts to rotate the molecule to align with p0 with E.
(E) In reality, the orientation into the field direction will be counteracted by random collision with other dipoles, and this process is energized by the thermal energy "KT".
(F) However, due to their thermal energy, molecules more around randomly and collide with each other and with the walls of container. These collisions destroy the dipole alignments.
(G) A snapshot of the dipoles in the in the materials in the presence of the field can be pictured. In which the dipoles have different orientations.
(H) Net average dipole moment per molecule is finite and directed along the field.
(I) A dipole at an angle θ to the field experiences a torque π that tries to rotate it. Work done by the field in rotating the dipole by dθ is πdθ.
E=π d θ