Electric Potential of the Body of Man Walking on Carpet

Abstract

This paper deals with the electric potential of human body measured by varying the kind of frictionable materials on which and with which one walks (carpets and foot-wear) and the manner and duration of walking in room air of 23°_??_25°C and 45_??_55% R. H. Any combination of the above factors gives the potential change approximately in the form v_bw{1-exp(-t/τ_bw)}. The saturation potential v_bw up to 3 kV is related linearly with the time constant τ_bw as
v_bw=[v_bw](1-τ_bw/[τ_bw]),
where [v_bw] and [τ_bw] are constants.
Depending upon the rubbing being hard or light, the coordinate system seems to be ([v_bw], 0) or (0, [τ_bw]). This phenomenon can be explained in terms of an equivalent circuit consisting of the internal resistance R that participates in the phenomenon and the load impedance R"C calculated from electric constants of the materials. From this equivalent circuit, [v_bw] and [τ_bw] are obtained as _??_v_bw and _??_τ_bw, respectively. Anti-static treatments such as application of surfactants and blending with rayon on carpet and conductive foot-wear are effective in lowering [v_bw].
The maximum potential of our body of 3 kV by walking with highly insulated foot-wear, the full capacity of the body of 90 pF in standing on one leg and the rubbing area of 150cm² give the charge density of 5.4esu/cm² which is of the order of corona density of 8.4esu/cm² on a parallel-plate condenser, suggesting that the corona discharge between carpet and foot-wear is responsible for such high density of charge in our body. When we reflect upon the fact that, for a highly insulated human. body of the capacity of 110 pF in standing on both legs to experience electric shock on the finger tip, body potential of at least 5 kV is needed, there. will be no such danger provided the room air temper-ature and humidity are not lower than the values used in this experiment. If otherwise, any foot-wear such as leather-soled shoes may conduct the generated charge to raise the body potential above the danger mark.