|MLA Citation:||Bloomfield, Louis A. "Question 1012"|
How Everything Works 21 Apr 2018. 21 Apr 2018 <http://howeverythingworks.org/print1.php?QNum=1012>.
However, a superconducting electromagnet is one in which the wires are superconducting—the current passing through them doesn't waste any power. Once a current has been started in a coil of superconducting wire, it flows forever. Since it doesn't waste any power, that current needs no source of power and produces no thermal energy. In fact, you can buy superconducting magnets with the current already started at the factory. As long as the wires are kept cold (as they must be to remain superconducting), the current will continue to flow and the coil will remain magnetic forever.