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NEET Sample Paper NEET Sample Test Paper-54

  • question_answer
    The temperatures of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x respectively are\[{{T}_{2}}\,\,and\,\,{{T}_{1}}({{T}_{2}}>{{T}_{1}})\]. The rate of heat transfer through the slab, in a steady state is \[\left( \frac{A({{T}_{2}}-{{T}_{1}})K}{x} \right)f,\,\,\,\]with \[f\] equal to-

    A) \[1\]     

    B)               \[1/2\]

    C)  \[2/3\]              

    D) \[1/3\]

    Correct Answer: D

    Solution :

    \[{{\operatorname{R}}_{eq}}\,=\,\,{{R}_{1}}\,\,+\,\,{{R}_{2}}\,\,\,{{K}_{eq}}\,\,=\,\,\frac{5K}{3}\] \[\frac{{{K}_{eq}}A({{T}_{2}}-{{T}_{1}})}{5x}\,\,=\,\,f\frac{\left[ A({{T}_{2}}-{{T}_{1}}) \right]}{x}\,\,.\,\,K\] \[f\,\,=\,\,\frac{1}{3}\]


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