KVPY Sample Paper KVPY Stream-SX Model Paper-10

  • question_answer
    In steady state, heat conduction equations governing heat flow are identical to the electric current flowing through a conductor. What are the dimensions of quantity analogous to electrical resistance?

    A) \[[M{{L}^{-2}}TK]\]                

    B) \[[{{M}^{-1}}{{L}^{-2}}TK]\]

    C) \[[M{{L}^{-\,2}}{{T}^{-\,3}}K]\]                   

    D) \[[{{M}^{-1}}{{L}^{-\,2}}{{T}^{3}}K]\]

    Correct Answer: D

    Solution :

    Electrical resistance, \[R=\frac{V}{I}\]
    So, heat resistance or thermal resistance is
    \[{{R}_{Th}}=\frac{\Delta T}{\Delta Q}\]
    where, \[\Delta T=\] temperature difference and \[\Delta Q=\] heat flow rate \[=\frac{H}{t}.\]
    \[\therefore \]\[{{R}_{Th}}=\frac{\Delta T}{\left( \frac{KA\Delta T}{l} \right)}\]\[\Rightarrow \]\[{{R}_{Th}}=\frac{l}{KA}\]
    So, its dimensions are
    \[[{{R}_{Th}}]=\frac{[L]}{[ML{{T}^{-\,3}}{{K}^{-1}}{{L}^{2}}]}=[{{M}^{-\,1}}{{L}^{-\,2}}{{T}^{3}}K]\]


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