Physical significance of dipole is that it is used to predict whether a molecule is polar or non polar.
In most molecules, the centre’s of positive charges and of negative charges lie at the same place. Therefore, their dipole moment is zero and that molecule is considered as non polar.
CO2 and CH4 are of this type of molecules. However, they develop a dipole moment when an electric field is applied.
But in some molecules, the centres of negative charges and of positive charges do not coincide. Therefore they have a permanent electric dipole moment, even in the absence of an electric field. Such molecules are called polar molecules.
A water molecule, H2O, is an example of this type
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