Physics

Physics

Problem

A cylindrical metal rod with emissivity 0.600.60 has radius 2.0 cm2.0\,\text{cm} and length 20 cm20\,\text{cm}. Its flat ends are closed. The rod is initially at a uniform temperature of 700 K700\,\text{K} and is placed in a very large, perfectly black surrounding kept at 0 K0\,\text{K} (so that re-absorption from surroundings may be neglected). Take σ=5.67×10−8 W m−2 K−4\sigma = 5.67\times10^{-8}\,\text{W\,m}^{-2}\,\text{K}^{-4}. a. (i) Compute the total surface area of the rod that is effective in emitting radiation. b. (ii) Calculate the amount of thermal energy it radiates in 5 min5\,\text{min}.

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