This is what I found (source):
I wonder about several things here.
First, why is tetrahydrothiophene's dipole moment bigger than that of tetrahydrofuran, when considering that tetrahydrofuran has an atom of stronger electronegativity?
Secondly, why thiophene has weaker dipole moment when the S atom has larger p obitals, and therefore, has weaker conjugation ability than O to aromatic ring. The result seems that S in thiophene has better conjugation effect. (that's why it has less stronger dipole.) and I don't seem to explain why.
So what are the reasons for these dipole moment orders?