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WB JEE Medical WB JEE Medical Solved Paper-2007

  • question_answer
    An ice box made of Styrofoam (Thermal conductivity \[=0.01\,J{{m}^{-1}}{{s}^{-1}}{{K}^{-1}}\] is used to keep liquids cool. It has a total wall area Including lid of \[\text{0}\text{.8}\,{{\text{m}}^{\text{2}}}\]and wall thickness of 2.0 cm. A bottle of water is placed in the box and filled with ice. If the outside temperature is \[\text{3}{{\text{0}}^{\text{o}}}\text{C}\] the rate of flow of heat into the box is (in\[\text{J}-{{s}^{-1}}\])

    A)  16                                         

    B)  14

    C)  12                                         

    D)  10

    Correct Answer: C

    Solution :

                     \[H=\frac{Q}{t}=\frac{KA({{\theta }_{1}}-{{\theta }_{2}})}{d}\] \[=\frac{0.01\times 0.8({{30}^{o}}-{{0}^{o}})}{2\times {{10}^{-2}}}\] \[=12\,J-{{s}^{-1}}\]


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