GerritJan Linker

Dipole moment  dependence on the origen Dipole moments are dependent on the choice of the origin when the system has an overall charge. When a system is neutral the dipole moment is not affected when another origin is chosen. Examples with discrete charges. 2 charges seperated at a distance 2: charge q1=1 at r1=(x,y)=(1,0) charge q2=+1 at r2=(x,y)=(1,0) Dipole moment m = q1*r1 + q2*r2 = 1*(1,0)+ 1*(1,0) = (2,0) Now, shift the origin by a translation vector (2,0): charge q1=1 at r1=(x,y)=(1,0) charge q2=+1 at r2=(x,y)=(3,0) Dipole moment m = q1*r1 + q2*r2 = 1*(1,0)+ 1*(3,0) = (2,0) Now, shift the origin again by a translation vector (0,2): charge q1=1 at r1=(x,y)=(1,2) charge q2=+1 at r2=(x,y)=(3,2) Dipole moment m = q1*r1 + q2*r2 = 1*(1,2)+ 1*(3,2) = (2,0) Clearly the dipole moment of a neutral system is not affected by the choice of the origin. When the system is not neutral overall this does not hold.
