A 420-W heating coil designed to operate from 110 V is made of Nichrome wire 0.520 mm in diameter. (Assume ? = 1.50 10-6 ? · m, and ? = 4.000 10-4(°C)-1 for Nichrome.)
(a) Assuming the resistivity of the Nichrome remains constant at its 20.0°C value, find the length of wire used.
(b) Now consider the variation of resistivity with temperature. What power is delivered to the coil of part (a) when it is warmed to 1 200°C?