The Mass of the Electric Carrier in Copper, Silver and Aluminium

Abstract

In a previous article [1] we have described some experiments in which a coil of copper wire was rotated about its axis at a high speed and then suddenly brought to rest, the ends of the coil being connected with a sensitive ballistic galvanometer which permitted a measurement of the pulse of current which was produced at the instant of stopping by the tendency of the electrons to continue in motion. We have continued these experiments making use of three new windings of copper wire, and using two different windings each of silver and aluminium wire. These further experiments were made not only because it seems desirable to subject so new a phenomenon to a more rigid test, but because it is also desirable to see if the mass of the carrier of electricity is the same in all different metals and how much it differs, if at all, from the mass of the electron in free space. The only change that we have made in our apparatus as described in the earlier article was to provide a small bowl-shaped metallic cover to protect the binding posts on the rotating wheel from air friction. This was particularly important when our coil mas of aluminium or silver in helping to reduce accidental thermoelectric forces which arose at the junction of the coil with the copper wires which led to the galvanometer.