NEET Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर NEET PYQ-Current Electricity Charging Capacitors

  • question_answer
    The charge flowing through a resistance R varies with time t as \[Q=at-b{{t}^{2}},\] where a and b are positive constants. The total heat produced in R is:                                                                                                          [NEET - 2016]

    A)  \[\frac{{{a}^{3}}R}{6b}\]      

    B)       \[\frac{{{a}^{3}}R}{3b}\]

    C)  \[\frac{{{a}^{3}}R}{2b}\]                  

    D)       \[\frac{{{a}^{3}}R}{b}\]

    Correct Answer: A

    Solution :

    [a] \[Q=at-b{{t}^{2}}\]
                \[i=a-2bt\]         {for \[i=0\Rightarrow \,t=\frac{a}{2b}\]}
                From joule's law of heating
    \[dH={{i}^{2}}Rdt\]
    \[H=\int\limits_{0}^{a/2b}{{{(a-2b)}^{2}}}Rdt\]
    \[H=\frac{{{(a-2b)}^{3}}R}{-3\times 2b}\left| _{0}^{\frac{a}{2b}} \right.=\frac{{{a}^{3}}R}{6b}\]
               


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