2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/21482We consider a simple phenomenological model of a semiconductor with absolute negative conductance in a magnetic field. We find the form of the domains of the electric field and current which arise as a result of an instability of a uniform state. We show that in both Corbino disc and Hall bar samples the residual conductance and resistance are negative and exponentially small; they decrease exponentially with increasing length L_{x,y}.7 pages, 3 Fig; typos corrected, references addedCondensed Mattertext