ABSTRACT
At temperatures below some critical temperature T c, many metals, alloys and doped semiconducting inorganic and organic compounds carry the electric current for infinite time without any applied electric field. Their thermodynamic and electromagnetic properties in the superconducting state (below T c) are dramatically different from the normal state properties above T c. Quite a few of them might be understood without any insight into the microscopic origin of superconductivity by exploiting the analogy between superconducting electrons and superfluid neutral helium atoms (liquid 4He flows without any friction below T c ≃ 2.17 K). Realizing this analogy, F and H London developed the successful phenomenological approach in 1935 describing the behaviour of superconductors in the external magnetic field. Ogg Jr proposed a root to high-temperature superconductivity introducing electron pairs in 1946 and Ginzburg and Landau proposed the phenomenological theory of the superconducting phase transition in 1950 providing a comprehensive understanding of the electromagnetic properties below T c.
