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JEE Main & Advanced JEE Main Paper (Held On 12-Jan-2019 Morning)

  • question_answer
    An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and resistance \[5\Omega .\] The value of R, to give a potential difference of mV across 10 cm of potentiometer wire is [JEE Main Online Paper Held On 12-Jan-2019 Morning]  

    A) \[490\,\Omega \]                        

    B) \[495\,\Omega \]

    C) \[395\,\Omega \]

    D)   \[480\,\Omega \]

    Correct Answer: C

    Solution :

    Let I be the current in the circuit \[4=(5+R)I\]         ?(i) According to given condition, \[5\times {{10}^{-3}}=\left( \frac{10}{100} \right)(5)(I)\]\[\Rightarrow \]\[I={{10}^{-2}}A\]                       ?(ii) Using (i) and (ii), 5+R=400\[\Rightarrow R=395\Omega \]              


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