Cool coils

MATERIALS that conduct electricity without losing any of it are the stuff that electricity companies dream of. In fact, they are far from being a pipe dream. All metals, as a Dutch physicist, Heike Kamerlingh Onnes, discovered in 1911, are capable of “superconducting”. But there is a small inconvenience. They do so only when refrigerated to a few Kelvin (K), just above absolute zero (-273°C), the coldest temperature possible. In practice it is therefore cheaper to let conductors waste some electricity than to keep them so cold.