12th Class Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank Case Based (MCQs) - Current Electricity

  • question_answer
    The resistivity of the material of a wire 1.0 m long, 0.4 mm in diameter and having a resistance of \[2.0\,\Omega \] is

    A) \[1.57\times {{10}^{-6}}\,\Omega m\]

    B) \[5.25\times {{10}^{-7}}\,\Omega m\]

    C) \[7.12\times {{10}^{-5}}\,\Omega m\]   

    D) \[2.55\times {{10}^{-7}}\,\Omega m\]

    Correct Answer: D

    Solution :

    (d) \[2.55\times {{10}^{-7}}\,\Omega m\]             \[l=1.0\,m;D=0.4\,mm=4\times {{10}^{-4}}m\]             \[R=2\,\Omega \]             \[A=\frac{\pi {{D}^{2}}}{4}=\frac{\pi \times {{(4\times {{10}^{-4}})}^{2}}}{4}=4\pi \times {{10}^{-8}}{{m}^{2}}\]             Now, \[\rho =\frac{RA}{l}=\frac{2\times 4\pi \times {{10}^{-8}}}{1}=2.55\times {{10}^{-7}}\Omega m\]


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