Silver conducts electricity better than any other substance.
It is also smooth and resists oxidation or rusting. These properties make it the essential contact metal in nearly every electrical system in the world, from a tiny hearing aid to the largest metropolitan power plants. The improvement from crank starting a car to simply turning a switch, for instance, was made possible partly by a button-like device, an electrical contact, about 90 percent silver and 10 percent cadmium. When you turn on the switch, the contact joins two metal lines so that an electric current flows from one line to another quickly, smoothly, and without building up excessive heat. Turn the switch off and the contacts separate, breaking the circuit, quickly and cleanly.