JEE Main & Advanced Physics Thermometry, Calorimetry & Thermal Expansion Question Bank Self Evaluation Test - Thermal Properties of Matter

  • question_answer
    A bar of iron is 10 cm at \[20{}^\circ C\]. At \[19{}^\circ C\]it will be (\[\alpha \]of iron\[=11\times {{10}^{-6}}/{}^\circ C\])

    A) \[11\times {{10}^{-6}}\] cm longer

    B) \[11\times {{10}^{-6}}\]cm shorter

    C) \[11\times {{10}^{-5}}\] cm shorter

    D) \[11\times {{10}^{-5}}\] cm longer

    Correct Answer: C

    Solution :

    [c] \[L={{L}_{0}}\left( 1+\alpha \,\Delta \theta  \right)\Rightarrow \frac{{{L}_{1}}}{{{L}_{2}}}=\frac{1+\alpha {{\left( \Delta \theta  \right)}_{1}}}{1+\alpha {{\left( \Delta \theta  \right)}_{2}}}\] \[\Rightarrow \frac{10}{{{L}_{2}}}=\frac{1+11\times {{10}^{-6}}\times 20}{1+11\times {{10}^{-6}}\times 19}\Rightarrow {{L}_{2}}=9.99989\] \[\Rightarrow \]Length is shorten by \[10-9.99989=0.00011=11\times {{10}^{-5}}\,cm.\]


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