Static Electrification of Filaments: Effect of Filament Diameter

- A study was made of the effect of filament diameter on the charge transferred between filaments rubbed together under controlled ambient and mechanical conditions. Filaments of various diameters and of medium resistivity (nylon, ∼ 10 12 ohm-cm.) were rubbed against a filament of low resistivity (tantalum, ∼ 10 -5 ohm-cm.) and one of high resistivity (polyethylene, ∼ 10 15 ohm-cm. ) at different normal forces between the fila ments. For nylon against tantalum, the charge transferred was found to be proportional to the square root of the product of the diameter and the normal force between the filaments. For nylon against polyethylene, the charge transferred was ound to be proportional to the square root of the normal force, but nearly independent of the diameter. These findings are consistent with the hypothesis that the charge transferred is proportional to the true area of contact (that is, the area over which interpenetration of molecular fields occurs) swept out on the object of lower conductivity.