JEE Main & Advanced Physics Transmission of Heat Question Bank Conduction

  • question_answer
    The ratio of the coefficient of thermal conductivity of two different materials is 5 : 3. If the thermal resistance of the rod of same thickness resistance of the rods of same thickness of these materials is same, then the ratio of the length of these rods will be                                                      [BHU 2000]

    A)            3 : 5                                          

    B)            5 : 3

    C)            3 : 4                                          

    D)             3 : 2

    Correct Answer: B

    Solution :

                       Thermal resistances are same                    Þ \[\frac{{{l}_{1}}}{{{K}_{1}}{{A}_{1}}}=\frac{{{l}_{2}}}{{{K}_{2}}{{A}_{2}}}\] Þ \[\frac{{{l}_{1}}}{{{K}_{1}}}=\frac{{{l}_{2}}}{{{K}_{2}}}\]\[(\because {{A}_{1}}={{A}_{2}})\]            Þ \[\frac{{{l}_{1}}}{{{l}_{2}}}=\frac{{{K}_{1}}}{{{K}_{2}}}=\frac{5}{3}\]


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