here I didn t understand last line how will current flow

Last updated: 6/21/2023

here I didn t understand last line how will current flow indefinitely without a voltage source i e potential difference Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature 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 Example Liquid Nitrogen