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I have seen a wide variety of different estimates for the maximum current rating for copper wire. For example, for 24-gauge copper wire, the Wikipedia article about "American wire gauge" claims that a copper wire will fuse after 10 s if carrying a current of over 29 A. On the other hand, this page claims a maximum current of only 3.5 A for chassis wiring and 0.577 A for power transmission. What is causing the disconnect between these wildly divergent estimates of the maximum current? Moreover, which of these estimates is most useful for estimating the maximum current that is safe for use in an electromagnet (both with and without insulation)?