In the present paper, we theoretically study the effect of density of state variation on the phenomena in the discontinuous magnetic field. Special attention is paid to the transient processes when the magnetic field is switched on (off). The difference in the density of states for the free 2D electron gas and the electron gas on under the magnetic field can lead to the occurrence of the electrostatic potential. Considering the transient phenomena of magnetic field switching, we obtain oscillating behavior of the electrostatic potential. The analysis includes two limit cases when the oscillation frequency of the electrostatic potential is low relative to the cyclotron frequency and when they are of the same order.