|Heike Kamerlingh Onnes physics
Lord Kelvin had speculated that electrical resistance would grow to infinity as the temperature of a metal approached absolute zero. Others, including Kamerlingh Onnes thought that resistance would steadily drop, but everyone was wrong. Onnes had been the first to liquify helium. Because of this expertise, he was able to conduct the experiment. Measuring the resistance of a solid mercury wire immersed in liquid helium, Onnes steadily decreased the temperature and found the resistance gradually decreased but then suddenly at 4.2 Kelvins fell to zero.
An yttrium-based cuprate perovskite material, yttrium barium copper oxide, was the first superconductive material that could be cooled below its transition state, 92 Kelvin, by liquid nitrogen, which is cheap to produce. At atmospheric pressure, liquid nitrogen boils at 77 Kelvin. Today one of the warmest cuprate superconductors is a ceramic composed of thallium, mercury, copper, barium, calcium, and oxygen that superconducts at 138 Kelvin, which is the same as minus 135.15 Celsius or minus 211.27 Farenheit, although some sources say that vanadium dioxide superconducts at about 340 Kelvin, and others claim superconductance at 28 Celsius with magnesium-doped oxycuprates for limited amperages at room temperatures.
The highest-temperature super- conductors today cannot easily be made into wire, and must be cooled far below zero, but the hope of room- temperature super-conductive wire, able to operate at one hundred degrees Celsius, remains a distant possibility possibly to be discovered by accident, but should save tremendous energy in power generation, lossless storage, free electrical transmission, reduce pollution, levitate trains, improve medical imaging. What games can you play with magnets? What doors would you open with keys that unlock any door?