Superconductivity
Alternate Name: Superconductors
Description: Superconductors are elements, alloys, or compounds that will conduct electricity without resistance below a certain temperature. Resistance is undesirable because it dissipates the energy in the circuit. Superconductivity is the feature of these materials that allows for electricity to flow forever in a closed circuit of it.
Superconductivity as a property was first observed in 1911 by Heike Kamerlingh Onnes. He discovered this phenomena by cooling mercury to the temperature where helium becomes liquid, or four degrees Kelvin. The Kelvin temperature scale has limits on temperature, and the lowest possible temperature that is thought to exist is zero degrees Kelvin. The corresponding temperature for four degrees Kelvin in Farenheight is -452 degrees, or -269 degrees Celsius. When Onnes cooled the mercury to four degrees Kelvin he realized that the resistance had dropped to zero, and electricity could flow through the material without loss of energy.
In 1933, it was found that superconducting materials will repel magnetic fields, this property being called diamagnetism. This property allows for a magnet to be levitated over a superconducting material. In later decades many other materials were found to be superconductive at low temperatures, and superconducting wires were developed. In the eighties a organic compound was synthesized to be capable of superconducting, and succeeded. This finding excited the scientific community, and opened up thoughts of designing compounds to perform in specific ways.
The next trend in studies of superconductors were to find materials that were capable of superconducting at higher temperatures. Currently, synthesized ceramics are found to be the best material for superconducting at higher temperatures, and the current record for the highest temperature is 138 degrees Kelvin. Researchers also believe that they could raise the temperature by twenty or thirty degrees by placing extreme pressures, up to 300,000 atmospheres on the ceramic.
Superconductors possess the quality of diamagnetism, and therefore repel magnetic fields. This also means that they levitate magnets over themselves. This fact sparked interest of possible applications in transit, and testing began for a train to run on superconducting magnets rather than conventional electromagnets. They possess advantages over electromagnets in the use of tracks due to the fact that with superconducting magnets, friction is eliminated between the train and the track. Electromagnetic tracks must also be physically larger, and also waste electrical energy as heat. As of recent, Japan constructed a test line to develop a train to run on superconducting magnets and on April 3, 1997 the train achieved a speed of 343 miles per hour. The wide spread use of this technology has been slowed due to the fact that very strong magnets, like those used in the tracks, are a bio-hazard.
Superconducting magnets have also found another use in medicine in the MRI. By subjecting the body to a strong superconductor-derived energy field to the body, hydrogen atoms in the body’s water and fat molecules are forced to accept energy. The emission of this energy can be detected and displayed on a computer, producing an image of the inside of the body.
Generators may be the next expansion of superconductors. Those that use superconducting wire are more than 99% efficient, which translates into less energy being used, and costs being reduced. In the latter part of 2002 General Electric received a 12.3 million dollar grant from congress to expand high temperature superconducting generators into production and commercialization. Another possible use for superconducting wire is in the replacement of underground copper power cables. With this replacement, more power could run through the wires, and the superconducting wires are space effective. In one example, 250 pounds of superconducting wire replaced 18,000 pounds of vintage copper wires, making it 7000% more space effective.
With all of the possible applications and advantages of superconducting materials discussed, one can only assume that they will become a bigger part of everyone’s life in the near future.
Bibliography:
- Superconductor Information for the Beginner. http://superconductors.org/
- The Nobel Foundation. Heike Kamerlingh Onnes - Biography. http://www.nobel.se/physics/laureates/1913/onnes-bio.html
Researcher: Kieran Collins (UCSC)