90CHAPTER 17 (b) The cost of operating the iron for 20 minutes is ()()561 kWh8.610J$0.080kWh$0.0191.9 cents3.6010JcostE rate=⋅=×==×17.51Ohm’s law gives the resistance as ()RVI= ∆. From RL Aρ=, the resistivity is given by ()RA Lρ=⋅. The results of these calculations for each of the three wires are summarized in the table below. ()mL()RΩ()mρΩ⋅0.540 10.4 61.4110−×1.028 21.1 61.5010−×1.543 31.8 61.5010−×The average value found for the resistivity is 6av1.47
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