The permanent dipole moment as the name suggests differs from induced polarization in that it is a permanent separation. They also differ in the fact that permanent dipole moments happen in polar not nonpolar molecules. These charges that separate balance out each other and therefore have a net charge of 0. The water molecule is an example of a permanent dipole moment. The permanent dipole moment is defined as the vector sum of the individual charge moments within the molecule.
Permanent dipole moments can be correlated with biological activities to obtain information about the physical parameters of molecules. The more soluble the molecule the easier it passes the lipoidal membranes of insects and attacks the insect's nervous system. Therefore the lower the dipole moment the greater the insecticidal action.