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

  • question_answer
    A system S receives heat continuously from an electrical heater of power 10 W. The temperature of S becomes constant at \[50{}^\circ C\]when the surrounding temperature is \[20{}^\circ C\]. After the heater is switched off; S cools from \[35.1{}^\circ C\] to \[34.9{}^\circ C\] in 1 minute. The heat capacity of S is       

    A) \[100J/{}^\circ C\]         

    B) \[300J/{}^\circ C\]

    C) \[750J/{}^\circ C\]         

    D)        \[1500J/{}^\circ C\]

    Correct Answer: D

    Solution :

    [d] Rate of loss of heat \[\propto \] difference in tem- perature with the surroundings. At\[50{}^\circ C,\frac{dQ}{dt}=k\left( 50-20 \right)=10\], where k = constant \[\therefore \operatorname{k}=l/3\] At an angle temperature of\[35{}^\circ C\], \[\frac{\operatorname{dQ}}{dt}=\frac{1}{3}\left( 35-20 \right)J/s=5J/s\] Heat lost in 1 minutes \[=\frac{dQ}{dt}\times 60J=5\times 60J=300J=Q\] Fall in temperature\[= 0.2{}^\circ C= AQ\]. \[\operatorname{Q}=c\Delta \theta .\]. Heat capacity \[=c=\frac{Q}{d\theta }=\frac{300J}{{{0.2}^{\operatorname{o}}}C}=1500J{{/}^{\operatorname{o}}}C.\]


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