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CMC Medical CMC-Medical VELLORE Solved Paper-2014

  • question_answer
    Charge passing through a conductor of crosssection area \[A=0.3\,{{m}^{2}}\] is given by \[q=3{{t}^{2}}+5t+2\] coulomb, where\[t\]is in second. What is the value of drift velocity at \[t=2\,s\] (Given \[n=2\times {{10}^{25}}/{{m}^{3}}\])

    A)  \[0.77\times {{10}^{-5}}m\text{/}s\]     

    B)  \[1.77\times {{10}^{-5}}m\text{/}s\]

    C)  \[2.08\times {{10}^{-5}}m\text{/}s\]     

    D)  \[0.57\times {{10}^{-5}}m\text{/}s\]

    Correct Answer: B

    Solution :

                    \[A=0.3{{m}^{2}}\] \[n=2\times {{10}^{25}}\text{/}{{m}^{3}}\] \[q=3{{t}^{2}}+5t+2\] \[i=\frac{dq}{dt}=6t+5=17\] \[i=neA{{v}_{d}}\] Drift velocity, \[{{v}_{d}}=\frac{i}{neA}=\frac{17}{2\times {{10}^{25}}\times 1.6\times {{10}^{-19}}\times 0.3}\]                   \[=\frac{17}{0.96\times {{10}^{6}}}\]   \[=1.77\times {{10}^{-5}}m\text{/}s\]


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