The Evolution of Capacitors [History]

A capacitor is a simple device. It is basically just two conductors sandwiched with an insulator between them. Engineers know the basic laws of physics: capacitance (the amount of charge) increases directly with the area of the conductors (plates), inversely with their distance apart, and directly with the dielectric constant of the insulation. Given a moment to think, engineers remember that the dielectric constant of air is one and that of pure water is 81. How did they find this out? The fascinating story goes back over two centuries.