## The Dipole Moment

Consider a system of electric chargesLet these have position vectorsrespectively with respect to an originThe dipole moment of this system of charges is

The centre of charge of the system is

The system of charges is neutral if

The dipole moment of a neutral system is independent of the origin. Supposeis the dipole moment with respect to an originand is the dipole moment with respect to an originwith

Thenandsince