A physical picture of the phenomena during the electronic oscillation in the magnetostatic oscillator is given. The notion of a critical radius for plate voltages varying between a larger and a smaller value than the critical voltage for a given constant magnetic field is developed. The value of the critical radius is calculated as a function of the voltage differences and the potential distribution. The flying time of the electrons is discussed in its relation to the voltage distribution, and the falling angle is expressed in a simple way.