12th Class Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank MCQ - Current Electricity

  • question_answer
              A wire has a resistance of \[2.5\,\Omega \] at \[28{}^\circ C\] and a resistance of \[2.9\,\Omega \] at \[100{}^\circ C\]. The temperature coefficient of resistivity of material of the wire is:

    A) \[1.06\times {{10}^{-3}}{}^\circ {{C}^{-1}}\]      

    B) \[3.5\times {{10}^{-2}}\,{}^\circ {{C}^{-1}}\]

    C) \[2.22\times {{10}^{-3}}\text{ }{}^\circ {{C}^{-1}}\]             

    D) \[3.95\times {{10}^{-2}}\text{ }{}^\circ {{C}^{-1}}\]

    Correct Answer: C

    Solution :

    (c) \[2.22\times {{10}^{-3}}\,{}^\circ {{C}^{-1}}\] Here,     \[{{R}_{1}}=2.5\,\Omega ,{{T}_{1}}=28{}^\circ C\] \[{{R}_{2}}=2.9\,\Omega \] and \[{{T}_{2}}=~100{}^\circ C\] As        \[{{R}_{2}}={{R}_{1}}[1+\alpha ({{T}_{2}}-{{T}_{1}})]\] \[\therefore 2.9=2.5[1+\alpha (100-28)]\]             \[\frac{2.9}{2.5}-1=72\alpha \] or \[\alpha =\frac{1}{72}\times \frac{2.9-2.5}{2.5}\]             \[=\frac{1}{72}\times \frac{0.4}{2.5}=2.22\times {{10}^{-3}}\,{}^\circ {{C}^{-1}}\]


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