Form and capacitance of parallel-plate capacitors

In basic electrostatics, the formula for the capacitance of parallel-plate capacitors is derived, for the case that the spacing between the electrodes is very small compared to the length or width of the plates. However, when the separation is wide, the formula for very small separation does not provide accurate results. In our previously published papers, we used the boundary element method (BEM) to derive formulas for the capacitance of strip and disk capacitors that are applicable even when the separation is large. In this paper, we present results and formulas for the capacitances of square and rectangular capacitors