JEE Main & Advanced Physics Transmission of Heat Question Bank Conduction

  • question_answer
    A slab consists of two parallel layers of copper and brass of the same thickness and having thermal conductivities in the ratio 1 : 4. If the free face of brass is at \[{{35}^{o}}C\] and that of copper at \[1:\sqrt{2.5}\], the temperature of interface is [IIT 1981; MP PMT 1987, 2001]

    A)            80°C                                         

    B)            20°C

    C)            60°C                                         

    D)            40°C

    Correct Answer: A

    Solution :

                       Temperature of interface q = \[\frac{{{K}_{1}}{{\theta }_{1}}+{{K}_{2}}{{\theta }_{2}}}{{{K}_{1}}+{{K}_{2}}}\] \[(\because \,\frac{{{K}_{1}}}{{{K}_{2}}}=\frac{1}{4}\Rightarrow \]If K1 = K then K2 = 4K) Þ \[\theta =\frac{K\times 0+4K\times 100}{5\,K}\]= 80°C


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