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
    Two conductors have the same resistance at \[0{}^\circ C\]but their temperature coefficients of resistance are\[{{\alpha }_{1}}\]and\[{{\alpha }_{2}}\]. the respective temperature coefficients of their series and parallel combinations are nearly - [AIEEE 2010]

    A) \[\frac{{{\alpha }_{1}}+{{\alpha }_{2}}}{2},\frac{{{\alpha }_{1}}+{{\alpha }_{2}}}{2}\]

    B) \[\frac{{{\alpha }_{1}}+{{\alpha }_{2}}}{2},{{\alpha }_{1}}+{{\alpha }_{2}}\]

    C) \[{{\alpha }_{1}}+{{\alpha }_{2}},\frac{{{\alpha }_{1}}+{{\alpha }_{2}}}{2}\]

    D) \[{{\alpha }_{1}}+{{\alpha }_{2}},\frac{{{\alpha }_{1}}{{\alpha }_{2}}}{{{\alpha }_{1}}+{{\alpha }_{2}}}\]

    Correct Answer: A

    Solution :

    [a] In series, \[{{R}_{1}}+{{R}_{2}}=Rs\]
    \[R(1+{{\alpha }_{1}}T)+R(1+{{\alpha }_{2}}T)=2R(1+{{\alpha }_{s}}T)\]
    \[2R+RT({{\alpha }_{1}}+{{\alpha }_{2}})=2R+2R\text{ }{{\alpha }_{s}}T\]
    \[{{\alpha }_{s}}=\frac{{{\alpha }_{1}}+{{\alpha }_{2}}}{2}\]
    In parallel\[\frac{1}{Rp}=\frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}}\]
    \[\frac{1}{\frac{R}{2}(1+{{\alpha }_{p}}T)}=\frac{1}{R(1+{{\alpha }_{1}}T)}+\frac{1}{R(1+{{\alpha }_{2}}T)}\]
    \[2(1-{{\alpha }_{p}}T)=1-{{\alpha }_{1}}T+1-{{\alpha }_{2}}T\]
    \[{{\alpha }_{p}}=\frac{{{\alpha }_{1}}+{{\alpha }_{2}}}{2}\]


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