So this sounds kind of weird to you, right? Well, let me start by explaining what a superconductor is and then we’ll see from there.
Superconducting materials are those that can conduct electricity with no resistance, so electrons just glide through a superconducting wire happily, unlike in a material such as copper where the electrons experience resistance and hence more power is needed to keep electrons flowing.
In magnetic resonance imaging – which is used in radiology to visualise internal structures of the body – superconducting material is arranged as a closed-loop coil. Since another consequence of being superconducting is that the material becomes magnetised – known as the Meissner effect – if you supply power to the material once and it’s in a closed loop, the electrons just keep going round and round, even if you then remove the power supply, and there you have it… a magnet that will stay on for some months.
They’re also using superconductors in the study of nuclear fusion, so they’re very important types of material. The small print to all of this, of course, is that you need to keep the superconducting material at temperatures close to absolute zero (4K with liquid helium), otherwise you will exceed the transition temperature by which this effect works.