Headline Jan 12, 2015/



IN 1908 a DUTCH physicist, Heike Kamerlingh Onnes, cooled helium gas to below its boiling point of  -269 degrees centigrade,  just four degrees above absolute zero (4k).

Three years later, exactly a century ago, he observed that liquid helium was used to chill mercury,  the metals  ''electrical resistance suddenly vanished'',  allowing current to flow completely unobstructed.

**He had discovered  superconductivity**.

The implications seemed nothing short of revolutionary. Perfectly efficient electric cables,  more powerful generators and motors,  magnetic levitation and a host of other technological wonders beckoned.

Since then most of these early hopes have been dashed. A hundred years on, superconductors have found widespread use in just one technology, magnetic resonance imaging (MRI)  -which lets doctors peer inside patients' bodies.

But this may be about to change, as materials which retain their remarkable properties at higher temperatures start to be put to work where Kamerlingh Onnes thought they belonged from the start in generating and transmitting electricity without resistance.

Electrical resistance arises when the free electrons passing through the rigid ionic lattice of a metal occasionally bump into its constituent ions. The collision transfers energy from the electron to the ion, which starts vibrating more vigorously as a result.

In other words, some electrical energy is lost as  heat (since the temperature of a substance is a measure of how furiously its atoms are vibrating).

In 1956 Leon Cooper, an American physicist, figured out that electrons in a superconductor avoid this fate by overcoming their mutual repulsion and pairing up.

As a negatively charged electrons passes through a lattice, the ions along its path feel a slight attractive force and stray as far into the electron's wake as the lattice structure lets them.

This distorts the lattice, creating a concentration of positive charge. Other electrons zipping along in the vicinity will then be drawn to this region, and, as a result, towards the original electron.

Normally, the pull of one passing electron on another is drowned out by the ions own wriggling. Cool the metal down enough, though, and the wriggling becomes sufficiently weak for one electron's gentle tug to be felt by another and for so called Cooper pairs to form.

Once paired, electrons stop behaving like ordinary particles of matter and together with other similar pairs, enter a quantum state in which they become oblivious to the ions, and so lose no energy bumping into them.

Current can than pass through the lattice without resistance.

The rub is that for Cooper pairs, cool enough means no more than about 30K, or -243 degrees C.

The only way to achieve temperatures that low involves the finicky and expensive process of liquefying helium. 

As a result, low-temperature superconductors are used only in devices where there is no substitute for their remarkable properties.

The Honour and Serving of the  ''operational research'' continues. Thank you for reading and see ya all on the next one. Superconductors research will continue to be published regularly. Never miss!

With respectful dedication to the Students, Professors and Teachers of the world. See Ya all on  !WOW!   -the World Students Society Computers-Internet-Wireless:

''' For All Generations '''

'''Good Night and God Bless

SAM Daily Times - the Voice of the Voiceless


Post a Comment

Grace A Comment!