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NEET Sample Paper NEET Sample Test Paper-69

  • question_answer
    The specific resistance of a wire is \[\rho \], its volume is \[3\text{ }{{m}^{3}}\] and its resistance is 3 ohms, then its length will be

    A) \[\sqrt{\frac{1}{\rho }}\]                                    

    B) \[\frac{3}{\sqrt{\rho }}\]

    C) \[\frac{1}{\rho }\,\,\sqrt{3}\]                  

    D) \[\rho \sqrt{\frac{1}{3}}\]

    Correct Answer: C

    Solution :

    \[Volume\,=\,\,A1\,\,=\,\,3\,\,\,\,\,\Rightarrow \,\,\,\,A=\frac{3}{l}\] Now \[R=\rho \frac{l}{A}\,\,\,\,\,\,\Rightarrow \,\,\,\,\,\,3=\frac{\rho \times l}{3/l}\,\,=\,\,\frac{\rho {{l}^{2}}}{3}\] \[\Rightarrow \,\,\,\,\,\,\,\,\,\,{{l}^{2}}=\frac{9}{\rho }=\frac{3}{\sqrt{\rho }}\]


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