Development of the lead vector concept.
(A) Because of linearity, the potential at a point P in the volume conductor is linearly proportional to dipoles in each coordinate direction.
(B) By superposition the potential at the point P is proportional to the sum of component dipoles in each coordinate direction. This proportionality is three-dimensional and can therefore be considered as a vector
, called lead vector.
(C) The potential at the point P is the scalar product of the source dipole
and the lead vector