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NEET Sample Paper NEET Sample Test Paper-52

  • question_answer
    A cylinder of radius R made of material of thermal conductivity \[{{K}_{1}}\] is surrounded by a cylindrical shell of inner radius R and outer radius 3R made of a material of thermal conductivity\[{{K}_{2}}\]. The two ends of the combined system are maintained at two different temperature. What is the effective thermal conductivity of the system?

    A) \[{{K}_{1}}+{{K}_{2}}\]                    

    B) \[\frac{{{K}_{1}}+8{{K}_{2}}}{9}\]

    C) \[\frac{{{K}_{1}}{{K}_{2}}}{{{K}_{1}}+{{K}_{2}}}\]                       

    D) \[\frac{8{{K}_{1}}+{{K}_{2}}}{9}\]

    Correct Answer: B

    Solution :

    \[\frac{1}{\operatorname{R}{{ & }_{eq}}}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}\] \[\frac{{{K}_{eq}}(9\pi {{R}^{2}})}{L}=\frac{{{K}_{1}}\pi {{R}^{2}}}{L}+\frac{{{K}_{2}}8\pi {{R}^{2}}}{L}\] \[{{K}_{eq}}\,\,=\,\,\frac{{{K}_{1}}+8{{K}_{2}}}{9}\]


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