JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर JEE PYQ-Current Electricity Charging and Discharging of Capacitors

  • question_answer
    Combination of two identical capacitors, a resistor R and a dc voltage source of voltage 6V is used in an experiment on a (C - R) circuit. It is found that for a parallel combination of the capacitor the time in which the voltage of the fully charged combination reduces to half its original voltage is 10 second. For series combination the time needed for reducing the voltage of the fully charged series combination by half is:  [AIEEE 11-05-2011]

    A) 10 second

    B) 5 second         

    C) 2.5 second

    D) 20 second

    Correct Answer: C

    Solution :

    [c] Time constant for parallel combination = 2RC
    Time constant for series combination \[=\frac{RC}{2}\]
    In first case:
    \[V={{V}_{0}}{{e}^{\frac{{{t}_{1}}}{2RC}}}=\frac{{{V}_{0}}}{2}\]                        …..(i)
    In second case:
    \[V={{V}_{0}}{{e}^{-\frac{{{t}_{2}}}{(RC/2)}}}=\frac{{{V}_{0}}}{2}\]                   ……(ii)
    From (i) & (ii),
    \[\frac{{{t}_{1}}}{2RC}=\frac{{{t}_{2}}}{(RC/2)}\]  \[\Rightarrow \]  \[{{t}_{2}}=\frac{{{t}_{1}}}{4}=\frac{10}{4}=2.5\sec .\]


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