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BCECE Engineering BCECE Engineering Solved Paper-2013

  • question_answer
    An electric kettle takes 4 A current a t220 V. How much time will it take to boil 1 kg of water from room temperature \[\text{20}{{\,}^{\text{o}}}\text{C?}\] (the temperature of boiling water is\[\text{100}{{\,}^{o}}\text{C}\])

    A)  12.6 min                             

    B)         12.8 min                             

    C)         6.3 min               

    D)         6.4 min

    Correct Answer: C

    Solution :

    Heat required,\[Q=1000\times 1\times \left( 100-20 \right)\] \[=1000\,\,\times \,\,80\,\text{cal}\] Heat produced in time t is, \[H=Vlt\] \[=220\times 4\times t\,\,J\] \[=\frac{220\times 4\times t}{4.18}\,\text{cal}\]                 \[\therefore \]  \[=\frac{220\times 4\times t}{4.18}=1000\times 80\]                 \[\Rightarrow \]               \[t=\frac{1000\times 80}{4.18\times 220\times 4}=6.3\,\min \]


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