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NEET Sample Paper NEET Sample Test Paper-28

  • question_answer
    Two rods of equal length and area of cross-section are kept parallel and lagged between temperatures \[{{20}^{o}}C\] and \[{{80}^{o}}C\]. The ratio of the effective thermal conductivity to that of the first rod is (the ratio of \[\frac{{{K}_{1}}}{{{K}_{2}}}=\frac{3}{4}\]):-

    A)  \[7:4\]                                 

    B)  \[7:6\]

    C)  \[4:7\]                                 

    D)  \[7:8\]

    Correct Answer: B

    Solution :

    For parallel combination (for two rods L = same and A = same) \[K=\frac{{{K}_{1}}+{{K}_{2}}}{2}=\frac{{{K}_{1}}+\frac{4}{3}{{K}_{1}}}{2}=\frac{7{{K}_{1}}}{6}\Rightarrow \frac{K}{{{K}_{1}}}=\frac{7}{6}\]


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