Calculation of electric field and force on conductor particles with a surface film

This paper applies the method of images, an analytical method, to calculate electric field on conductor particles with a surface film. The method utilizes the multipole re-expansion and appropriate fundamental solutions. Electric field is repetitively calculated so as to satisfy all the boundary conditions. The main advantage over numerical field-calculation methods is that high accuracy can be realized as neither approximation nor discretization of the particle surface or the film thickness is involved. The calculation results for arrangements of a particle chain under a uniform field show the field intensification due to the film thickness and electrical properties. We have also carried out field calculation by the boundary element method (BEM), and compared the results with the analytical ones. The results by the BEM exhibit higher error with decreasing film thickness. Force and yield stress have been calculated from the electric field and compared with experimental results. The comparison shows a good agreement for the ac field, but significant difference for the dc one.