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10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    An electrical heater has resistance of \[12\Omega \] and is operated from 220 volts power line. If no heat escapes from it how much time is required to raise the temperature of 40 kg of water from \[10{}^\circ C\] to \[80{}^\circ C\]?

    A)  1456 seconds     

    B)         1828 seconds

    C)  2708 seconds       

    D)         3250 seconds

    Correct Answer: C

    Solution :

     Heat required\[=(40\times {{10}^{3}})\times 1\times (80-15)\] Now,     \[H=\frac{{{V}^{2}}t}{R\times 4.2}cal\] \[\Rightarrow \]               \[t=\frac{HR\times 4.2}{{{V}^{2}}}\]                   \[=\frac{26\times {{10}^{5}}\times 12\times 4.2}{220\times 220}\]                  \[=\mathbf{2708}\]seconds.


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