The Orientation Effect of Rigid Dipoles

A dipole molecule (see p. 29) behaves at large distances as a neutral structure. However, on approach sufficiently close to be comparable with the distance d between the two charges, say, to 4 or 5 A, the separation between those charges becomes significant. The particle can then influence similar particles by attraction between the unlike poles of each. 

The equations for the dipole attraction may easily be derived from purely electrostatic considerations, and it will suffice here to describe the 

It is presupposed that the distance r between the molecular centers of gravity is large compared with the distance between the charges d in any 

The meaning of this can be shown in an example the dipole moment of the H2O molecule amounts to about 1.8 X lO on dividing by the unit charge of 4.8 X 10 e.s.u., we obtain, according to the equation 

Since a grouping which is established under the influence of the dipole force is always counteracted by thermal agitation, the orientation effect is highly dependent upon temperature. 

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