{"id":488,"date":"2019-07-31T15:38:59","date_gmt":"2019-07-31T15:38:59","guid":{"rendered":"http:\/\/nitk.acm.org\/blog\/?p=488"},"modified":"2019-07-31T15:38:59","modified_gmt":"2019-07-31T15:38:59","slug":"superconductivity","status":"publish","type":"post","link":"https:\/\/nitk.acm.org\/blog\/2019\/07\/31\/superconductivity\/","title":{"rendered":"Superconductivity"},"content":{"rendered":"

Superconductivity is the phenomenon of a material having exactly zero resistance and expulsion of magnetic flux. This happens when a certain material is cooled below its critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes<\/a> on April\u00a08, 1911, in Leiden<\/a>. This is a quantum mechanical phenomenon and is characterized by the Meissner effect. The Meissner effect put simply it is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state.<\/p>\n

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For most metals electric resistance of a metallic conductor decreases with decreasing temperature. In normal conductors such copper and silver this decrease is limited due to the presence of impurities. However in a superconductor the resistance drops abruptly to zero when the material is cooled below its critical temperature. Mercury, Niobium-Tin, Lanthanum-Barium-Copper Oxide are examples of materials that showcase superconductivity.<\/p>\n

Now what makes superconductivity so interesting?<\/p>\n

Firstly superconductors have zero electrical DC resistance. This allows them to maintain an electric current near indefinitely with no power source. It has been experimentally proven that the current existing in these coils can persist for years without any visible degradation.<\/p>\n

In conventional superconductors, the electronic fluid cannot be resolved into individual electrons. Instead, it consists of bound pairs<\/em> of electrons known as Cooper pairs<\/a>. This pairing is caused by an attractive force between electrons from the exchange of phonons<\/a>. Due to quantum mechanics<\/a>, the energy spectrum<\/a> of this Cooper pair fluid possesses an energy gap<\/em><\/a>, meaning there is a minimum amount of energy \u0394E<\/em> that must be supplied in order to excite the fluid. Therefore, if \u0394E<\/em> is larger than the thermal energy<\/a> of the lattice, given by kT<\/em>, where k<\/em> is Boltzmann’s constant<\/a> and T<\/em> is the temperature<\/a>, the fluid will not be scattered by the lattice. The Cooper pair fluid is thus a superfluid<\/a>, meaning it can flow without energy dissipation.<\/p>\n

The second interesting property is the Meissner effect. When a superconductor is placed in a weak external magnetic field<\/a> H<\/strong>, and cooled below its transition temperature, the magnetic field is ejected. The Meissner effect does not cause the field to be completely ejected but instead the field penetrates the superconductor but only to a very small distance, characterized by a parameter\u00a0\u03bb<\/em>, called the London penetration depth<\/a>, decaying exponentially to zero within the bulk of the material. The Meissner effect<\/a> is a defining characteristic of superconductivity. For most superconductors, the London penetration depth is on the order of 100\u00a0nm.<\/p>\n

The Meissner effect is sometimes confused with the kind of diamagnetism<\/a> one would expect in a perfect electrical conductor: according to Lenz’s law<\/a>, when a changing<\/em> magnetic field is applied to a conductor, it will induce an electric current in the conductor that creates an opposing magnetic field. In a perfect conductor, an arbitrarily large current can be induced, and the resulting magnetic field exactly cancels the applied field.<\/p>\n

The Meissner effect is distinct from this\u2014it is the spontaneous expulsion which occurs during transition to superconductivity. Suppose we have a material in its normal state, containing a constant internal magnetic field. When the material is cooled below the critical temperature, we would observe the abrupt expulsion of the internal magnetic field, which we would not expect based on Lenz’s law.<\/p>\n

Now we\u2019ve got a base on superconductivity let\u2019s talk applications<\/h4>\n

Superconducting magnets are some of the most powerful magnets known. They\u2019re popularly used in MRI\/NMR machines, mass spectrometers and for beam steering in particle accelerator.<\/p>\n

Superconductors is an MRI machine<\/a> commonly found in hospitals. Only a superconductive system could allow the energy required to generate a magnetic field that powers an MRI, which can be anywhere from 2,500 times to 10,000 times the strength of Earth\u2019s magnetic field, to be economical.<\/p>\n

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Almost all transmission of electricity is via copper wire. For reference in the US alone 6% of electricity is lost during the transmission process. That equates a loss of nearly 10 billion dollars just because of intrinsic resistance. HTS power cables which is a high temperature superconductor which provides 0% loss of electrical current during electrical transmission. In the US multiple places use HTS cables to save grid efficiency<\/p>\n

All that\u2019s cool but let\u2019s talk about the future.<\/p>\n

The EM drive<\/strong> was invented by the British engineer Roger Shawyer in 2000. Now what is the EM drive. It\u2019s a chamber that converts electricity into electromagnetic microwaves inside a specially designed chamber that exhibits measurable thrust. The superconducting EM drive could reach 60% the speed of light. Although this technology is years away is theorised that this will be powerful enough to lift a car.<\/p>\n

Superconducting elevators take advantage of the Meisner effect and use a series of Linear Induction Motors<\/a> to accelerate the magnetically levitating elevators cabins vertically and horizontally. The world tallest building in Dubai, Burj Khalifa, will seem trivial in height in the coming decades.<\/p>\n

It costs a lot of money to send anything into space, billions<\/a> are spent yearly to send satellites into LEO and the International Space Station (ISS) has exceeded over $125 billion in costs. And because of cost, StarTram<\/a> is still considered by overwhelming majority as unfeasible in today\u2019s world. But StarTram would make it possible to send cargo and passengers into Low Earth Orbit.<\/p>\n

The principles behind StarTram involves 100\u2019s of miles of connected tubes evacuated of air that would reach 14 miles into the atmosphere. A SkyTram space portal would be located at a mountain range a few miles above sea level (e.g. Mongolia) to negate some of the cost of connecting the tubes from sea level to 20 miles high. SkyTram\u2019s tubes will be lined with permanent magnets while SkyTram\u2019s superconducting maglev pods will be able to accelerate through the evacuated tubes (no air resistance) at well over Mach 20 to reach LEO.<\/p>\n

 <\/p>\n

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These are just some of the crazy applications and potential superconductivity holds not to mention the consequences and challenges it poses to quantum mechanics.<\/p>\n

-Abhinav Pavithran<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Superconductivity is the phenomenon of a material having exactly zero resistance and expulsion of magnetic flux. This happens when a certain material is cooled below its critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes on April\u00a08, 1911, in Leiden. This is a quantum mechanical phenomenon and is characterized by the Meissner effect….<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[10,26],"tags":[],"class_list":["post-488","post","type-post","status-publish","format-standard","hentry","category-tech","category-vidyut"],"_links":{"self":[{"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/posts\/488","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/comments?post=488"}],"version-history":[{"count":4,"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/posts\/488\/revisions"}],"predecessor-version":[{"id":498,"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/posts\/488\/revisions\/498"}],"wp:attachment":[{"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/media?parent=488"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/categories?post=488"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nitk.acm.org\/blog\/wp-json\/wp\/v2\/tags?post=488"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}