The most difficult step in the analysis of the capacitance of arbitrarily shaped conductingplates is the determination of the electric center, or the expansion point of the charge density. This paper presents the generalized Huygens' principle, which indicates that the charge distribution on a conducting plate of convex shape has a tendency to be a circle before approachingthe fringe. Therefore, the center of the largest extended circle can be taken as the electric center. The agreement with numerical methods is demonstrated.
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