On the Measurement of the Ratio of the Gravitational and Inertial Masses of an Electron

The motion of an electron in an experiment similar to that of Witteborn–Fairbank is discussed. It is demonstrated that the gravitational force acting on an electron is not compensated by the Barnhill–Schiff force and the acceleration acquired by it in the gravitational field of the Earth is proportional to the ratio of its passive gravitational mass to the inertial mass only if this electron is weakly relativistic or relativistic. Therefore, experiments with relativistic or weakly relativistic electrons are needed in order to measure this ratio.