JEE Main & Advanced Physics Thermometry, Calorimetry & Thermal Expansion Question Bank Topic Test - Thermometry, Thermal Expansion and Calorimetry (3-5-21)

  • question_answer
    Three liquids with masses \[{{m}_{1}},\,{{m}_{2}},\,{{m}_{3}}\] are thoroughly mixed. If their specific heats are \[{{c}_{1}},\,{{c}_{2}},\,{{c}_{3}}\] and their temperatures \[{{T}_{1}},\,{{T}_{2}},\,{{T}_{3}}\] respectively, then the temperature of the mixture is

    A) \[\frac{{{c}_{1}}{{T}_{1}}+{{c}_{2}}{{T}_{2}}+{{c}_{3}}{{T}_{3}}}{{{m}_{1}}{{c}_{1}}+{{m}_{2}}{{c}_{2}}+{{m}_{3}}{{c}_{3}}}\]

    B) \[\frac{{{m}_{1}}{{c}_{1}}{{T}_{1}}+{{m}_{2}}{{c}_{2}}{{T}_{2}}+{{m}_{3}}{{c}_{3}}{{T}_{3}}}{{{m}_{1}}{{c}_{1}}+{{m}_{2}}{{c}_{2}}+{{m}_{3}}{{c}_{3}}}\]

    C) \[\frac{{{m}_{1}}{{c}_{1}}{{T}_{1}}+{{m}_{2}}{{c}_{2}}{{T}_{2}}+{{m}_{3}}{{c}_{3}}{{T}_{3}}}{{{m}_{1}}{{T}_{1}}+{{m}_{2}}{{T}_{2}}+{{m}_{3}}{{T}_{3}}}\]

    D) \[\frac{{{m}_{1}}{{T}_{1}}+{{m}_{2}}{{T}_{2}}+{{m}_{3}}{{T}_{3}}}{{{c}_{1}}{{T}_{1}}+{{c}_{2}}{{T}_{2}}+{{c}_{3}}{{T}_{3}}}\]

    Correct Answer: B

    Solution :

                  
    Let the final temperature be \[T{}^\circ C\].
    Total heat supplied by the three liquids in coming down to
    \[0{}^\circ C\] = \[{{m}_{1}}{{c}_{1}}{{T}_{1}}+{{m}_{2}}{{c}_{2}}{{T}_{2}}+{{m}_{3}}{{c}_{3}}{{T}_{3}}\]           ..... (i)
    Total heat used by three liquids in raising temperature from
    \[0{}^\circ C\] to \[T{}^\circ C\] = \[{{m}_{1}}{{c}_{1}}T+{{m}_{2}}{{c}_{2}}T+{{m}_{3}}{{c}_{3}}T\]  .....(ii)
    By equating (i) and (ii) we get
    \[({{m}_{1}}{{c}_{1}}+{{m}_{2}}{{c}_{2}}+{{m}_{3}}{{c}_{3}})\,T\]
    = \[{{m}_{1}}{{c}_{1}}{{T}_{1}}+{{m}_{2}}{{c}_{2}}{{T}_{2}}+{{m}_{3}}{{c}_{3}}{{T}_{3}}\]
    \[\Rightarrow \] \[T=\frac{{{m}_{1}}{{c}_{1}}{{T}_{1}}+{{m}_{2}}{{c}_{2}}{{T}_{2}}+{{m}_{3}}{{c}_{3}}{{T}_{3}}}{{{m}_{1}}{{c}_{1}}+{{m}_{2}}{{c}_{2}}+{{m}_{3}}{{c}_{3}}}\].


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