  A point charge is frequently approximated by various charge distributions
deriving the Lorentz-Abraham-Dirac (LAD) equation. Here a rigid spherical shell
is treated from this point of view. This particular continuum model is
excellent to investigate whether some hidden expectations are true or not. It
is shown here that the field of a uniformly charged rigid spherical shell
cannot be substituted by the field of a central point charge. The related
calculations are short and transparent due to a reference frame free
representation of spacetime and the mathematical theory of generalised
functions. %Here it is shown that the field of a uniformly charged rigid
spherical shell cannot be substituted by the field of a central effective point
charge. The related calculations are short and transparent due to a reference
frame free representation of spacetime and the mathematical theory of
generalised functions.
