NEET Sample Paper NEET Sample Test Paper-9

  • question_answer Two litres of water of at initial temperature of \[{{27}^{o}}C\] is heated by a heater of power 1KW in a kettle. If the lid of the kettle is open, then heat energy is lost at a constant rate of\[160J/s\]. The time in which the temperature will rise from \[{{27}^{o}}C\] to \[77{}^\circ C\] is (specific heat of water\[=4.2\text{ }KJ/kg\]):

    A)  \[5\text{ }min\text{ }20\text{ }s\]                  

    B)  \[8\text{ }min\text{ }20\text{ }s\]

    C)  \[10\text{ }min\text{ }40\text{ }s\]                

    D)  \[12\text{ }min\text{ }50\text{ }s\]

    Correct Answer: B

    Solution :

    As, heat gained by water = Heat supplied - heat loss \[ms\Delta \theta =1000t-100t\](by the question)             \[t=\frac{2\times 4200\times 50}{840}=8\,\min \,20s\]


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