Welcome to brain Stuff from house stuff works dot com, where smart happens. I am Marshall Brand with today's question, what is superconductivity. Super Conductivity is something that scientists have known about for decades. In several medals, if you cool them down to near zero degrees kelvin, they will become super conducting, meaning that they will lose their electrical resistance. Zero degrees kelvin is the same as minus four nine
degrees fahrenheit or minus two seventy degrees celsius. It's about as cold as anything can get, and if you have liquid helium, it gets down near zero degrees kelvin. So if you immerse a metal like zinc or aluminum, or tin or mercury in liquid helium, they will become superconductors.
The temperature at which a material loses its electrical resistance is called the critical temperature, and recently scientists have found several ceramic materials which have much higher critical temperatures, like the temperature of liquid nitrogen. This is important because liquid helium is really expensive, while liquid nitrogen has a cost that's roughly equal to the cost of milk. Superconductivity is a big deal because electricity is an important part of
our lives. Because superconductive materials have no electrical resistance, meaning electrons can travel through them freely. They can carry large amounts of electrical current for long periods of time without losing energy is heat. Superconducting loops of wire have been shown to carry electrical currents for several years with no
measurable loss. This property could be a big deal for electrical power transmission if trans mission lines can be made of superconducting ceramics, and it could also have a big effect on things like storage of electricity, because in theory, you could store electricity and a superconducting loop and hold it there for years. Another property of a superconductor is that once the transition from the normal state to the
superconducting state occurs, external magnetic fields can't penetrate it. This effect is called the Meisner effect and it has implications for making high speed magnetically levitated trains. It also has implications for making powerful, small superconducting magnets for magnetic resonant imaging. So this brings up an obvious question, how do electrons travel through superconductors with no electrical resistance. Let's take a
look at this a little more closely. The atomic structure of most metals is a lattice structure, much like a windows screen, in which the intersection of each set of perpendicular lines is an atom. Metals hold onto their electrons quite loosely, so these particles can move freely through this lattice. This is why metals conduct heat and electricity very well to begin with. As electrons move through a typical metal in the normal state, they collide with atoms and lose
energy in the form of heat. In a superconductor, the electrons travel in pairs and move quickly between the atoms with a lot less energy loss. As a negatively charged electron moves through the space between two rows of positively charged atoms, like the wires in a windows screen, it pulls inward on the atoms. This distortion attracts a second electron to move in behind it. This second electron encounters less resistance, much like a passenger car following a truck
on the freeway encounters less air resistance. The two electrons form a weak attraction, travel together in a pair, and encounter less resistance overall. In a superconductor, electron pairs are constantly forming, breaking and reforming. But the overall effect is that electrons flow with little or no resistance. The low temperature makes it easier for the electrons to pair up.
One final property of superconductors is that when two of them are joined by a thin insulating layer, it's easier for the electron pairs to pass from one superconductor to another without resistance. This is known as the DC Josephson effect, and you may have heard of the Josephson junction. This effect has implications for super fast electrical switches that can
be used to make small, high speed computers. The future of superconductivity research is defying materials that can become superconductors at room temperature. Once this happens, the whole world of electronics, power, and transportation could be completely revolutionized. For more on this and thousands of other topics, visit how stuffworks dot com and don't forget to check out the brain stuff blog
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