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A copper rod of length 20 cm and cross-sectional area 0.20 cm² has its left end held at 20 deg C and its right end at 80 deg C. Neglecting radiation losses, find the temperature at a point 11 cm from the left end and the heat current through the rod. (Thermal conductivity of copper = 385 W/m-degC.)

1. 53 deg C and 2.31 J/s
2. 47 deg C and 2.31 J/s
3. 53 deg C and 4.62 J/s
4. 47 deg C and 4.62 J/s

Correct answer: 53 deg C and 2.31 J/s

Solution

Linear interpolation gives T(11 cm) = 20 + 60*(11/20) = 53 deg C, and H = 385 * 0.20e-4 * 60 / 0.20 = 2.31 J/s.

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