In physics we study about conductivity, but there is another phenomenon exist in superconductor Known as superconductivity. There is many physical properties observed in superconductors. There is a certain temperature exists, known as critical temperature below which electrical resistance vanishes and magnetic field is expelled from that particular material. A superconductor has a Characteristic, critical temperature below which the resistance drops very quickly and becomes zero at this temperature. An electrical current through a loop of superconductor wire can remain Indefinitely aalthough there is no power source.
shabenoor (Mon,) studied this question.