SUPERCONDUCTORS
Introduction
Before Kamerlign Onnes,
in 1908, was able to liquefy helium and bring its temperature down to about
1K, it had been known that the resistance of a metal falls when cooled below
room temperature. However, it was not known what value the resistance would
approach if the temperature was reduced towards 0K until Onnes, while experimenting
with platinum, discovered that, its resistance fell when cooled to a very
low value that depended on the metal’s purity.
As the temperature of mercury was reduced
toward 0K, the value of the resistance would fall smoothly until the resistance
fell extremely suddenly at about 4K. Below 4K, mercury passed into a new
state with electrical properties unlike those previously known: this new state
that mercury had entered was called the “superconducting state.”
Introduction to Superconductors
Basic
Conditions
The
Resistance in a Superconductor
The
Two Types of Superconductors