The disappearance of electrical conductivity in many metals at certain critical
temperature gave a boost to the hope of people thinking about powerful
electromagnets and other electrical technologies. They thought, if a
specimen can take current without any Ohmic (resistive) losses then the dream of
constructing high-field electromagnets can be fulfilled. In 1913, Onnes
fabricated a small coil of Lead keeping this in mind and cooled it down to its
superconducting state, i.e. below 4.2 K. What was driven him to do so was -- he
wanted to flow high current through it without significant power loss, and
generate high magnetic field. However, he along with the entire science
community were greatly disappointed when it was found that the magnet was unable
to produce more than few hundred Gauss even when it is operated below its
superconducting temperature. Above a certain field, it was behaving as if a normal conductor is being charged with current. This superconducting to normal transition was termed as
quench. With the help of further investigations, it was found
that the superconducting behavior of the metals was also disappearing at a certain
field generated either internally or externally (few hundred Gausses). Thus, to
the disappointment of all, it was found that the superconductors can be operated
within the critical temperature and critical field (which was too low to make an
electromagnet).
For straight superconductors carrying high current, the quenching occurs when the field generated at the surface of the wire crosses the critical field.
THIS WAS AN INITIAL SET-BACK TO THE SCIENTIFIC COMMUNITY.
For straight superconductors carrying high current, the quenching occurs when the field generated at the surface of the wire crosses the critical field.
THIS WAS AN INITIAL SET-BACK TO THE SCIENTIFIC COMMUNITY.
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