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JEE Main & Advanced JEE Main Paper (Held On 11-Jan-2019 Morning)

  • question_answer
    In a Wheatstone bridge (see fig), Resistances P and Q are approximately equal. When \[R=400\Omega ,\]the bridge is balanced. On interchanging P and Q, the value of R, for balance, is \[405\Omega ,\]The value of X is  close to [JEE Main Online Paper (Held On 11-Jan-2019 Morning]

    A) 401.5 ohm                    

    B) 404.5 ohm

    C) 403.5 ohm      

    D)                  402.5 ohm

    Correct Answer: D

    Solution :

    For a balanced bridge,\[\frac{P}{Q}=\frac{400}{X}\]        ...(i) After interchanging P and Q,\[\frac{P}{P}=\frac{405}{X}\]            ...(ii) Multiplying both the equations, \[X=\sqrt{{{R}_{1}}{{R}_{2}}}=\sqrt{400\times 405}=402.5\Omega \]


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