Superconductivity – one of the fundamental linking mechanisms in an unlimited and connected universe.

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature.

The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature.

If mercury is cooled below 4.1 K, it loses all electric resistance. This discovery of superconductivity by H. Kammerlingh Onnes in 1911 was followed by the observation of other metals which exhibit zero resistivity below a certain critical temperature. The fact that the resistance is zero has been demonstrated by sustaining currents in superconducting lead rings for many years with no measurable reduction. An induced current in an ordinary metal ring would decay rapidly from the dissipation of ordinary resistance, but superconducting rings had exhibited a decay constant of over a billion years!

The superconducting state can be destroyed by a rise in temperature or in the applied magnetic field, which then penetrates the material and suppresses the Meissner effect. From this perspective, a distinction is made between two types of superconductors. Type-I materials remain in the superconducting state only for relatively weak applied magnetic fields. Above a given threshold, the field abruptly penetrates into the material, shattering the superconducting state. 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 is infinitely more than a physics phenomena of the first order. It may be one of the fundamental linking mechanisms in an unlimited and connected universe.

The fascinating phenomenon of superconductivity and its potential applications have attracted the attention of scientists, engineers and businessmen. Intense research has taken place to discover new superconductors, to understand the physics that underlies the properties of superconductors, and to develop new applications for these materials. In this unit you will read about the history of superconductors, taking a brief look at their properties. You will also learn about modelling the properties of superconductors and the two different types of superconductor that exist today.
Superconducting electromagnets produce the large magnetic fields required in the world’s largest particle accelerators, in MRI machines used for diagnostic imaging of the human body, in magnetically levitated trains (Figure 8) and in superconducting magnetic energy storage systems. But at the other extreme superconductors are used in SQUID (superconducting quantum interference device) magnetometers, which can measure the tiny magnetic fields (~10−13T) associated with electrical activity in the brain, and there is great interest in their potential as extremely fast switches for a new generation of very powerful computers.The fascinating phenomenon of superconductivity and its potential applications have attracted the attention of scientists, engineers and businessmen. Intense research has taken place to discover new superconductors, to understand the physics that underlies the properties of superconductors, and to develop new applications for these materials. In this unit you will read about the history of superconductors, taking a brief look at their properties. You will also learn about modelling the properties of superconductors and the two different types of superconductor that exist today. Superconducting electromagnets produce the large magnetic fields required in the world’s largest particle accelerators, in MRI machines used for diagnostic imaging of the human body, in magnetically levitated trains (Figure 8) and in superconducting magnetic energy storage systems. But at the other extreme superconductors are used in SQUID (superconducting quantum interference device) magnetometers, which can measure the tiny magnetic fields (~10−13T) associated with electrical activity in the brain, and there is great interest in their potential as extremely fast switches for a new generation of very powerful computers.

for more details visit: http://www.superconductors.org/