Superconductors
o Superconductors are metallic materials that are "pure" conductors of electricity at extreme temperatures. That is, at specified temperatures, superconductors produce precisely zero resistance to an electrical current. There are many materials with superconductive properties at certain temperatures. Some common superconductors include tin, aluminum, nitrogen, mercury, lead, zinc, helium, uranium and titanium. The temperature at which superconductor materials demonstrate zero electrical resistance varies between materials. Another important property of superconductors is that, at the specified temperature, a superconductor requires no applied voltage to maintain its current for an indefinite period.