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

  • question_answer
    An iron tyre is to be fitted on to a wooden wheel 1m in diameter. The diameter of tyre is 6 mm smaller than that of wheel. The tyre should be heated so that its temperature increases by a minimum of (the coefficient of cubical expansion of iron is\[3.6\times {{10}^{-5}}/{}^\circ C\])             

    A) \[167{}^\circ C\]

    B) \[334{}^\circ C\]

    C) \[500{}^\circ C\]

    D) \[1000{}^\circ C\]

    Correct Answer: C

    Solution :

    [c] Initial diameter of tyre =(1000- 6) mm = 994 mm, so initial radius of tyre \[\operatorname{R}=\frac{994}{2}=497mm\]  and change in diameter AD = 6 mm so \[\Delta R=\frac{6}{2} = 3 mm\] After increasing temperature by \[\Delta \theta \]tyre will fit onto wheel Increment in the length (circumference) of the iron tyre  \[\Delta L=L\times \alpha \times \Delta \theta =L\times \frac{\gamma }{3}\times \Delta \theta \]\[[As\,\,\alpha =\frac{\gamma }{3}]\]\[2\,\pi \,\Delta R=2\pi R\left( \frac{\gamma }{3} \right)\Delta \theta \Rightarrow \Delta \theta \]   \[=\frac{3}{\gamma }\frac{\Delta \,R}{R}=\frac{3\times 3}{3.6\times {{10}^{-5}}\times 497}\Rightarrow \Delta \theta \simeq {{500}^{\circ }}C\]


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