How does superconductor work

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From the perspective of how they behave in magnetic fields, however, scientists commonly classify them into two groups. A Type I superconductor is usually made of a pure metal.

When cooled below its critical temperature, such a material exhibits zero electrical resistivity and displays perfect diamagnetism , meaning magnetic fields cannot penetrate it while it is in the superconducting state. Type II superconductors are usually alloys, and their diamagnetism is more complex. To understand why, we need to look at how superconductors respond to magnetism.

Just as every superconductor has a critical temperature that makes or breaks its superconducting state, each is also subject to a critical magnetic field. A Type I superconductor enters and leaves the superconducting state at one such threshold, but a Type II material changes states twice, at two different magnetic field thresholds.

The distinction between Type I and Type II materials resembles the difference between dry ice solid carbon dioxide and water ice. Both solids cool well, but they handle heat differently: Water ice melts into a mixed state, ice water, whereas dry ice sublimates : At normal pressure, it transitions directly from solid to gas. With respect to magnetism, a Type I superconductor is like dry ice: When exposed to its critical field, its superconductivity burns off instantly.

A Type II is more versatile. Raise the magnetic field above a certain threshold, however, and the material reorganizes into a mixed state -- a vortex state in which small whirlpools of superconducting current flow around islands of normal material. Like ice water, it still does its job pretty well. If the magnetic field strength rises, however, the islands of normalcy grow together, thus destroying the surrounding whirlpools of superconductivity.

What does this mixed state mean for magnetism? We've discussed what happens when a superconductor gets warm. Now, let's look at it from the other direction. In their normal, warm states, both Type I and Type II materials allow magnetic fields to flow through them, but as they cool toward their critical temperatures, they increasingly expel these fields; electrons in the material set up eddy currents that produce a counter-field, a phenomenon known as the Meissner effect.

When they reach their critical temperature, Type I superconductors evict any remaining magnetic field like so many deadbeat roommates. Depending on the strength of the magnetic field in which they exist, Type II fields might do the same -- or they might get a little clingy. If they're in a vortex state , the magnetic field that still flows through the islands of normal material in their superconducting streams can become stuck, a phenomenon known as flux pinning see sidebar Magnetic flux is a measure of the amount of magnetic field passing through a given surface.

Because they can remain superconductors in this stronger magnetic field, Type II materials like niobium-titanium NbTi make good candidates for the type of superconducting magnets found in, say, Fermilab's proton accelerator or in MRI machines. In , Andre Geim and Sir Michael Berry won the Ig Nobel Prize for Physics by levitating a frog, as well as water and hazelnuts, using a superconductor and diamagnetism. Although we tend to think of water and organic tissue as nonmagnetic, some elements and most compounds exhibit a very weak repulsive effect when placed in a strong magnetic field.

Physicists also use diamagnetism to stably levitate superconductors. The trick lies in Type II superconductors like yttrium barium copper oxide, which allow some magnetic field through and pin it in place. The "quantum levitation" video that went viral on the web in exemplified this kind of levitation, in which magnetism and diamagnetism combine to hold the levitator perfectly still, unlike Type I materials, which levitate steadily but wobble, or ferromagnets, which cannot levitate stably without outside help.

The industrial and scientific applications of superconductors are limited by the special temperature conditions they require to work their electromagnetic mojo, so it makes sense to classify materials based on their critical temperatures and pressure requirements. Hundreds of substances, including 27 metallic elements -- such as aluminum, lead, mercury and tin -- become superconductors at low temperatures and pressures. Another 11 chemical elements -- including selenium, silicon and uranium -- transition to a superconductive state at low temperatures and high pressures [source: Encyclopaedia Britannica ].

Until , when IBM researchers Karl Alexander Mulller and Johannes Georg Bednorz ushered in the age of high-temperature superconductors with a barium-lanthanum-copper oxide that achieved zero resistance at 35 K minus C, minus F , the highest critical temperature achieved by a superconductor measured 23 K minus C, minus F. Such low-temperature superconductors required cooling by liquid helium, which was difficult to produce and tended to break budgets [source: Haldar and Abetti ].

High-temperature superconductors bring the temperature range up to around K minus C, minus F , meaning they can be cooled using liquid nitrogen made cheaply from air [source: Mehta ]. Although physicists understand the mechanisms governing low-temperature superconductors, which follow the BCS model, high-temperature superconductors remain enigmatic [source: CERN ].

The holy grail would be to achieve a material with zero resistance at room temperature, but thus far that dream remains elusive. Perhaps it cannot be done or, perhaps, like other scientific revolutions, it lies just over the horizon, awaiting the necessary technological or theoretical innovation to make the dream a reality.

In the meantime, the powerful advantages that superconductors offer suggest a wide array of present and future applications in the areas of electric power, transportation, medical imaging and diagnostics, nuclear magnetic resonance NMR , industrial processing, high energy physics, wireless communications, instrumentation, sensors, radar, high-end computing and even cryogenics [source: CCAS ].

In addition to the maglev , MRI and particle accelerator applications we mentioned earlier, superconductors are currently used commercially in NMR spectroscopy, a key tool for biotechnology, genomics, pharmaceutical research and materials science work. Industry also applies them in a magnetic process for separating kaolin clay, a common filler in paper and ceramic products. As for the future, if researchers and manufacturers can overcome superconductors' limitations of cost, refrigeration, reliability and acceptance, the sky's the limit.

Some see green technologies, such as windmills, as the next step in a more widespread acceptance and application of the technology, but larger possibilities loom. Who knows? Conversely, Type-II superconductors tolerate local penetration of the magnetic field, which enables them to preserve their superconducting properties in the presence of intense applied magnetic fields. This behaviour is explained by the existence of a mixed state where superconducting and non-superconducting areas coexist within the material.

Type-II superconductors have made it possible to use superconductivity in high magnetic fields, leading to the development , among other things, of magnets for particle accelerators.

Superconductivity Below a certain temperature, materials enter a superconducting state and offer no resistance to the passage of electrical current. Three names, three letters and an incomplete theory Conventional physics does not adequately explain the superconducting state and neither does the elementary quantum theory of the solid state, which treats the behaviour of the electrons separately from that of the ions in the crystalline lattice.

Some of the properties are given below:. In a superconductive state, superconductors illustrate zero electric resistance or infinite electric conductivity.

As we know, when the material is cooled under its transition temperature, then its resistance will be reduced to zero. It happens due to the creation of copper bonds inside the metal. The copper bonds provide an ideal path to flow the electric current.

The Meissner effect is a property of all superconductors that was discovered by two physicists Walther Meissner and Robert Ochsenfeld in As per this effect, relatively weak magnetic fields are completely repulsed from the interior of all superconductors except for a surface layer.

It is also known as critical temperature. The transition temperature is the range of temperature in which an ordinary conductor changes its conducting state from normal to superconducting. Most of the superconductors have a transition temperature range between 1 Kelvin and 10 Kelvin. When the current flows in a superconductor it generates a magnetic field.

As the value of the flowing current increases, the magnetic field also gets increased. When the flowing current crosses a certain value then its superconductivity gets distorted. The value of the minimum current that can be passed in a specimen without destroying its superconductivity is known as Critical current.

When the two superconductors are divided with the help of thin-film in insulating material, then they form a junction of low resistance to find the electrons with copper bonds. The copper bond electrons tunnel from one surface of the junction to the other surface. Due to the flow of electrons, an electric current flows between these two superconductors. This current is known as Josephson current and this is the Josephson effect.

At present time we are using superconductors in several areas to serve human kinds. Some of them are given below:. How does Superconductor work? What is the superconductor?

History of superconductivity: The Discovery of superconductivity was a revolutionary achievement.