Krista Lum 3a
Dipole moments arise from differences in electronegativity (so in nearly all molecules except diatomic molecules between two atoms of the same element--N2, H2, O2...etc.). When one atom has a stronger pull for electrons, partial charges are created. One atom might have a partial positive and another atom might have a partial negative, and they will attract each other electrostatically.
Covalent bonds (except for diatomic molecules between two atoms of the same element--N2, H2, O2, etc) will also have partial charges because there is a difference in electronegativity. This means there will be dipole moments, moments where the positve and negative ends line up and electrostatically attract because of the difference in pull. Thus, covalent bonds will have dipole moments.
To calculate it,
where mu is the dipole moment
q is the magnitude of the charge (absolute value of it)
and r is the distance between the charges