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Superconductivity is a state of matter that chemical elements, compoundsand alloys assume on being cooled to temperatures near to absolutezero. Hence, a superconductor is a solid material that abruptlyloses all resistance to the flow of electric current when cooled below acharacteristic temperature. This temperature differs for different materials butgenerally is within the absolute zero (-273° C). Superconductors have thermal, electric and magnetic properties that differ fromtheir properties at higher temperatures and from properties ofno superconductive materials.

Nowhundreds of materials are known to become superconductors at lowtemperature. Approximately 26 of the chemical elements are superconductors. Among these are commonly known metals such as aluminum, tin, lead and mercury and several less common ones.

Most of the known superconductors are alloys or compounds.

It ispossible for a compound to be superconducting even if the chemical elements constituting it are not.

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New Hope for Energy Recently some ceramic materials have been found to be super­conductors. Superconducting ceramics are substances which can transmit electriccurrents with no loss of energy at temperatures much higher thanconventional superconductors (that is, at the temperature of liquid

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