The breakdown electric field between two conducting spheres by the method of images

The determination of the breakdown electric field of air between two identical conducting spheres is a good example of the use of the method of images to solve a practical problem in engineering electromagnetics. The sparkover electric field is computed from published or measured data for the breakdown voltage by using the theoretical solution for the image charges. Thus students are exposed to a sophisticated method of images solution involving two sets of infinitely many charges. Additional educational benefits include an enhanced appreciation for the properties of air as an insulator, for the limits of the electroquasistatic approximation, for the numerical convergence properties of infinite series, and for the history of science. Instead of using published tables, an exposure to high-voltage engineering to obtain measured breakthrough data is an option if a suitable laboratory is available.