Cobalt, the metal in magnets and phone batteries, is synonymous with the colour blue. But what exactly are magnets, how do they work and where are they used? And is some of the cobalt being mined by children? Presenter Laurence Knight hears from chemistry professor Andrea Sella of University College London why a permanent magnet is like a flock of birds, and he travels to Arnold Magnetics near Sheffield where manager Martin Satyr explains how magnets are used in everything from recovering the he...
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