JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank Mock Test - Current Electricity

  • question_answer
    For the arrangement shown in figure, the switch is closed at t = 0. The time after which the current becomes \[2.5\mu A\]is given by (take ln2 = 0.69)

    A) 10 s                 

    B) 5 s        

    C) 7 s       

    D) 0.693 s

    Correct Answer: C

    Solution :

    [c] In the case of discharging, \[I={{I}_{0}}{{e}^{-t/RC}}\] or \[2.5\times {{10}^{-6}}=\frac{{{q}_{0}}}{RC}{{e}^{-1/RC}}=5\times {{10}^{-6}}{{e}^{-t/10}}\] or \[{{e}^{t/10}}=2\] Taking log on both sides, we get \[\frac{t}{10}=ln\,2\]or \[t=10\,ln\,2=6.9\cong 7s\]          


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