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Cell["Problem 5.7 (Engel)", "Title"],

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  "Compare the maximum safe current density in a piece of copper wire with \
the current density that flows through the tip of a typical STM probe. For \
copper wire, assume a diameter of 3 mm and a maximum safe current of 20 A. \
For the STM, assume a probe tip diameter of 1 nm and a current of ",
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  " The current ",
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piece of standard copper wire (the kind that would handle most of the \
electricity in your home, for example)."
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