AMU Medical AMU Solved Paper-2000

  • question_answer
    Two vessels of different materials are identical in size and wall thickness, they are filled with equal quantities of ice at \[0{}^\circ C\]. If the ice melts completely in 10 and 25 min respectively, then the coefficients of thermal conductivities of the material are

    A)  2 : 3                                      

    B)  3 : 5

    C)  5 : 2                                      

    D)  1 : 1

    Correct Answer: C

    Solution :

                     The quantity of heat flowing in the vessel is same, hence                 \[Q=\frac{{{K}_{1}}\,A\,({{\theta }_{1}}-{{\theta }_{2}})\,{{t}_{1}}}{d}\]                 \[=\frac{{{K}_{2}}\,A\,({{\theta }_{1}}-{{\theta }_{2}})\,{{t}_{2}}}{d}\] Where \[{{\theta }_{1}}\] and \[{{\theta }_{2}}\] are temperatures of the outer and the inner walls of the two vessels. From this, we have                 \[{{K}_{1}}{{t}_{1}}={{K}_{2}}{{t}_{2}}\] \[\Rightarrow \]               \[\frac{{{K}_{1}}}{{{K}_{2}}}=\frac{{{t}_{2}}}{{{t}_{1}}}=\frac{25}{20}=\frac{5}{2}\]


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