where the effect of interference during a scattering event is neglected. One can rewrite (2.26) as

Using the formula for the resistance given by (2.25) and (2.27), one can see that the resistance of the wire is additive, . Applying this result to the case of scatterers yields

where is an average transmission probability for an individual scattering event over a mean free path. Thus the total resistance is given by a series connection of microscopic resistances. This is nothing but OHM's law, according to which the microscopic resistance is proportional to .