Uncertainties in Measurements of Specific Charge (e/m) of the Electron (2nd report)

Abstract

The measurement of specific charge of an electron in student physics experiments always tended to give the values larger than the literature value. We considered that this was caused by the loss of kinetic energy due to the collision of the electron with helium atoms in the instrument tube and constructed a mean free path model for the electron to derive the theoretical equation. However, it was found that the measured values were obviously different from the literature value even when precise measurements were performed under the measurement conditions that were expected to yield the literature value. We concluded that the systematic error was caused by the loss of kinetic energy of the electron in the electron gun, and that it was difficult to accurately determine the specific charge with this experimental method.