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

  • question_answer
    A wire of resistor R is bent into a circular ring of radius r. Equivalent resistance between two points X and Y on its circumference, when angle XOY is a, can be given by

    A)            \[\frac{R\alpha }{4{{\pi }^{2}}}(2\pi -\alpha )\]

    B)            \[\frac{R}{2\pi }(2\pi -\alpha )\]

    C)            R (2p ? a)

    D)            \[\frac{4\pi }{R\alpha }(2\pi -\alpha )\]

    Correct Answer: A

    Solution :

                       Here \[{{R}_{XWY}}=\frac{R}{2\pi r}\times (r\alpha )=\frac{R\alpha }{2\pi }\]    \[\left( \because \,\alpha =\frac{l}{r} \right)\] and  \[{{R}_{XZY}}=\frac{R}{2\pi r}\times r(2\pi -\alpha )=\frac{R}{2\pi }(2\pi -\alpha )\] \[{{R}_{eq}}=\frac{{{R}_{XWY}}{{R}_{XZY}}}{{{R}_{XWY}}+{{R}_{XZY}}}=\frac{\frac{R\alpha }{2\pi }\times \frac{R}{2\pi }(2\pi -\alpha )}{\frac{R\alpha }{2\pi }+\frac{R(2\pi -\alpha )}{2\pi }}\]\[=\frac{R\alpha }{4{{\pi }^{2}}}(2\pi -\alpha )\]


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