Question

A substance has zero resistance below 1 K. What is such a substance called?

• A. Superconductor.
• B. conductor
• C. semiconductor
• D. insulator

Answer 1

The correct option is A Superconductor.

A superconductor is a material that can conduct electricity or transport electrons from one atom to another with no resistance. This means no heat, sound or any other form of energy would be released from the material when it has reached "critical temperature" (Tc), or the temperature at which the material becomes superconductive.
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. An electric current flowing through a loop of superconducting wire can persist indefinitely with no power source.
Materials that will form superconductors come in two basic varieties, those which are metals or alloys of metals and the newer variety that are ceramic-like materials.
Some examples in the metal category are Mercury, Niobium, Tin, Lead and various alloys and the second category includes the more complex compounds Lanthanum-Barium-Copper Oxide and Yttrium-Barium-Copper Oxide.
Hence, superconductor is the substance whose has zero resistance below 1K.