JEE Main & Advanced Physics Thermometry, Calorimetry & Thermal Expansion Question Bank Calorimetry

  • 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 °C. Total heat supplied by the three liquids in coming down to 0°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 0oC to ToC            = \[{{m}_{1}}{{c}_{1}}T+{{m}_{2}}{{c}_{2}}T+{{m}_{3}}{{c}_{3}}T\]                  .....(ii) By equating (i) and (ii) we get \[({{m}_{1}}{{c}_{1}}+{{m}_{2}}{{c}_{2}}+{{m}_{3}}{{c}_{3}})\,T\] = \[{{m}_{1}}{{c}_{1}}{{T}_{1}}+{{m}_{2}}{{c}_{2}}{{T}_{2}}+{{m}_{3}}{{c}_{3}}{{T}_{3}}\] Þ \[T=\frac{{{m}_{1}}{{c}_{1}}{{T}_{1}}+{{m}_{2}}{{c}_{2}}{{T}_{2}}+{{m}_{3}}{{c}_{3}}{{T}_{3}}}{{{m}_{1}}{{c}_{1}}+{{m}_{2}}{{c}_{2}}+{{m}_{3}}{{c}_{3}}}\].


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