NEET Physics Thermometry, Calorimetry & Thermal Expansion Question Bank Mock Test - Thermal Properties of Matter

  • question_answer
    A solid whose volume does not change with temperature floats in a liquid. For two different temperatures \[{{t}_{1}}\] and \[{{t}_{2}}\] of the liquid, fractions \[{{f}_{1}}\]and \[{{f}_{2}}\]of the volume of the solid remain submerged in the liquid. The coefficient of volume expansion of the liquid is equal to

    A) \[\frac{{{f}_{1}}-{{f}_{2}}}{{{f}_{2}}{{t}_{1}}-{{f}_{1}}{{t}_{2}}}\]         

    B) \[\frac{{{f}_{1}}-{{f}_{2}}}{{{f}_{1}}{{t}_{1}}-{{f}_{2}}{{t}_{2}}}\]

    C) \[\frac{{{f}_{1}}+{{f}_{2}}}{{{f}_{2}}{{t}_{1}}-{{f}_{1}}{{t}_{2}}}\]       

    D) \[\frac{{{f}_{1}}+{{f}_{2}}}{{{f}_{1}}{{t}_{1}}-{{f}_{1}}{{t}_{2}}}\]

    Correct Answer: A

    Solution :

    [a] As with the rise in temperature, the liquid undergoes volume expansion therefore the fraction of solid submerged in liquid increases. Fraction of solid submerged at \[{{t}_{1}}{}^\circ C={{f}_{1}}=\] Volume of displaced liquid \[={{V}_{0}}(1+\gamma {{t}_{1}})\]                                       (i) and fraction of solid submerged at \[{{t}_{2}}{}^\circ C={{f}_{2}}=\] Volume of displaced liquid \[={{V}_{0}}(1+\gamma {{t}_{2}})\]                 (ii) From Eqs. (i) and (ii), \[\frac{{{f}_{1}}}{{{f}_{2}}}=\frac{1+\gamma {{t}_{1}}}{1+\gamma {{t}_{2}}}\Rightarrow \gamma =\frac{{{f}_{1}}-{{f}_{2}}}{{{f}_{2}}{{t}_{1}}-{{f}_{1}}{{t}_{2}}}\]


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