  The wide use of a speed-independent distance as a cut-off impact parameter
together with Rutherford's scattering formula, within the cut-off theory, to
account for charge screening in plasma environment embodies a clear
inconsistency. A new physically justified choice of the cut-off distance is
introduced and used to derive a closed form expression for the effective
momentum transport cross section. A simple approximation for the present
Coulomb logarithm, free of special functions, is also presented and assessed. A
comparison with experimentally recovered data for the reduced Coulomb
conductivity showed better agreement and better physical behavior of the
present expressions compared to previous cut-off expressions in the literature.
