Sharp edges and precise measurements

Practical electrodes may have rounded or diffuse edges, but their counterparts used in modelling have well defined sharp edges. We show the effect of the high field at the sharp edge in three situations: (a) an improved computation of the edge capacitance of strip and disc capacitors (b) a calculation of surface currents which shows that conduction alone cannot account for the observed absorption currents (c) an approach to the problem of the field in edge-plane and point-plane electrode configurations. These examples indicate that a wider range of model calculations and greater numerical accuracy are needed as an aid to interpreting experimental data.