Electrification of an elastic sphere by repeated impacts on a metal plate

Impact electrification between an elastic sphere and a metal plate has been studied experimentally. To find out how charge transfers between the conta ct bodies, the voltage profiles at the impact are measured under various ex perimental conditions using a digital oscilloscope, and simultaneously the contact deformation of the sphere is visualized with a high-speed camera. T he initial charge on the sphere and the transferred charge are obtained fro m the integrated voltage with respect to the elapsed time of the impact pro cess. The variation of the electrification by repeated impacts is analysed by taking account of the initial charge and charge relaxation with elapsed time. Furthermore, the relationship between the transferred charge and the contact area as a function of the impact velocity is investigated based on the electrification theory and Hertz analysis of elastic contact deformatio n.