Question

what is superconductivity and define critical temperature​

Answer 1

Answer:

Superconductivity is the ability of certain materials to conduct electric current with practically zero resistance. ... For a material to behave as a superconductor, low temperatures are required. Superconductivity was first observed in 1911 by H. K. Onnes, a Dutch physicist.

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a critical point is the end point of a phase equilibrium curve. The most prominent example is the liquid-vapor critical point, the end point of the pressure-temperature curve that designates conditions under which a liquid and its vapor can coexist