The current density jB of a species B in a given point of the solution is obtained by multiplying the flux density of that species at the given point by the Faraday constant F and by the charge number z B of the species: \[j_{\mathbf{B}} = z_{\text{B}}\ F\ N_{\mathbf{B}}\] where jB is a vector which indicates the direction in which the charges transported by the species B flow and which gives the number of these charges going through a plane oriented perpendicular to the vector, divided by time and by area, and N B is the flux density of a minor constituent of the solution with respect to a fixed frame of reference.