NEET Sample Paper NEET Sample Test Paper-35

  • question_answer
    When resistance of wire of \[\text{50 }\!\!{}^\circ\!\!\text{ C}\] is \[5R\Omega \] and at \[{{100}^{o}}C\]is\[6R\Omega \]. Find resistance at\[{{0}^{o}}C\].

    A)  \[1R\Omega \]             

    B)  \[8R\Omega \]

    C)  \[3R\Omega \]             

    D)  \[4R\Omega \]

    Correct Answer: D

    Solution :

    From relation,   \[{{R}_{1}}={{R}_{0}}\,(1+\alpha \Delta t)\] Case I:      \[5R={{R}_{0}}(1+\alpha \times 50)\]      ?..(i) Case II:      \[6R={{R}_{0}}(1+\alpha \times 100)\]    .....(ii) On dividing equation (i) by equation (ii) we get. \[\frac{5}{6}=\frac{1+50\,\alpha }{1+100\,\alpha }\] \[\Rightarrow \] \[5\times (1+100\alpha )=6\times (1+50\alpha )\] \[\Rightarrow \] \[5+500\alpha =6+300\alpha \] \[\Rightarrow \] \[200\alpha =1\] \[\alpha =\frac{1}{200}\Omega {{/}^{o}}C\] On substituting in equation (i) we get, \[5R={{R}_{0}}\,\left( 1+\frac{1}{4} \right)\] \[\Rightarrow \]   \[5R=\frac{5}{4}{{R}_{0}}\] \[\Rightarrow \]  \[{{R}_{0}}=4R\Omega \]


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