experiments that proved that the conductivity of metals is due to free electrons. The experiments were performed in 1912 by L. I. Mandel’shtam and N. D. Papaleksi, whose experimental results were not published, and in 1916 by the American physicists T. Stewart and R. Tolman.
In the experiments a large-diameter coil wound with a metal conductor was rapidly rotated and then abruptly stopped. Owing to inertia, however, the free charges in the conductor continued to move for a period of time. The charges’ motion relative to the conductor produced a transitory electric current in the coil. This current was registered with a galvanometer connected to the ends of the coil by means of sliding contacts. The direction of the current indicated that the current was a result of the ordered motion of negatively charged particles. The magnitude of the transferred charge was calculated to be directly proportional to the charge mass ratio of the particles creating the current. Measurements then demonstrated this ratio to be equal to that obtained for the electron in other experiments.