The giant magnetoresistance (GMR) effect allows drives like this one, less than an inch in diameter, to detect the tiny magnetic fields that store data in portable electronic devices.
This is a cylinder composed solely of carbon atoms, and one of its properties is good electrical conductivity. In effect, nanotubes act as wires a few billionths of a metre in diameter.
这是一种仅由碳原子组成的圆柱体，其中一个特性就是具有很好的导电性。
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Use diameter 500 super big mirror roller, iron effect much better.