 Therefore, if superconductive wire is made into a closed loop, current flows around the loop forever.Superconductors require cooling to temperatures near 4K with liquid helium for most metallic superconductors like niobium–tin alloys, or cooling to temperatures near 77K with liquid nitrogen for the expensive, brittle and delicate ceramic high temperature superconductors.Nevertheless, there are many technological applications of superconductivity, including superconducting magnets.