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NEET Sample Paper NEET Sample Test Paper-87

  • question_answer
    Time required to boil 2 litres of water initially at \[20{}^\circ C\] by a heater coil which works at 80% efficiency spending 500 joule/s is

    A) 82 minutes        

    B)        50 minutes

    C) 28 minutes        

    D)        37 minutes

    Correct Answer: C

    Solution :

    [c] Heat required to boil water \[=mc\Delta q\] \[=2\times 4200\times (100-20)\] \[=6.72\times {{10}^{3}}\,J\] If t be the time of boil then \[\eta \times 500\times t=6.72\times {{10}^{3}}\] or   \[t=\frac{6.72\times {{10}^{3}}}{0.8\times 500}=28\,\text{minutes}\text{.}\]


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