A quasi one-dimensional steady-state model of the Hall thruster is presented. For given mass flow rate, magnetic field profile and discharge voltage the unique solution can be constructed, assuming that the thruster operates in one of the two regimes: with or without the anode sheath. It is shown that for a given temperature profile the applied discharge voltage uniquely determines the operating regime: for discharge voltages greater than a certain value, the sheath disappears. That result is obtained over a wide range of incoming neutral velocities, channel lengths and widths and cathode plane locations. A good correlation between the quasi 1-D model and experimental results can be achieved by selecting an appropriate temperature profile. We also show how the presented model can be used to obtain a two-dimensional potential distribution.