, the dielectric is
polarised The extent of polarisation depends on the relative strength of
two mutually opposite factors: the dipole potential energy in the external
field tending to align the dipoles with the field and thermal energy tending
to disrupt the alignment There may be, in addition, the  ‘induced dipole
moment’ effect as for non-polar molecules, but generally the alignment
effect is more important for polar molecules Thus in either case, whether polar or non-polar, a dielectric develops
a net dipole moment in the presence of an external field