Consider a 1000-W iron whose base plate is made of 0.5-cm-thick aluminum alloy 2024-T6 (Æ¿ = 2770 kg/m3 and cp = 875 J/kg·oC). The base plate has a surface area of 0.03 m2. Initially, the iron is in thermal equilibrium with the ambient air at 22oC. Assuming 90 percent of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 200oC.

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FIGURE P4-81