Using new techniques and novel materials, scientists have learned to construct permanent magnets of astonishing power. Into a small hunk of fancy alloy, or a little bit of fragile ceramic, they have built all the pulling power of a hefty electromagnet without its awkward current-carrying coils. But in spite of their handiness. the new magnets have a built-in flaw: their pull is permanent. They lack practical versatility because their fierce attraction for iron-bearing metal cannot be turned off at will, unlike the clumsiest electromagnet, which can be controlled by the flick of...
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