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Knows that different kinds of materials respond differently to electric forces; in some materials, such as metals, electrons flow easily, whereas in insulating materials, such as glass, they can hardly flow at all; semiconducting materials have intermediate behavior, and at low temperatures some materials become superconductors and offer no resistance to the flow of electrons.

Automatic Windshield Wipers

A caller on an automotive-themed radio program asked for help with a problem. It seems that when it rained her windshield wipers sometimes turned themselves on. How is this possible?

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