  The elementary processes taking place in the formation of charged particles
and their flow in parallel-plane, cylindrical and spherical ionization chambers
are considered. On the basis of particles and charges balance a differential
equation describing the distribution of current densities in the ionization
chamber volume is obtained. As a result of the differential equation solution
an analytical form of the current-voltage characteristic of an ionization
chamber with homogeneous ionization is obtained. For the parallel-plane case
the comparison with experimental data is performed.
