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Haryana PMT Haryana PMT Solved Paper-2011

  • question_answer
    125 cm of potentiometer wire balances the emf of a cell and 100 cm of the wire is required to    balance the poles of a cell which are joined by a  20 resistor. The internal resistance of the cell is

    A)                  0.250                                   

    B)  0.500

    C)                  0.750                                   

    D)  1.250

    Correct Answer: B

    Solution :

                    Here,    \[{{l}_{1}}\]= 125 cm, \[{{l}_{2}}\]= 100 cm                 R=2\[\Omega \]                 Internal resistance                 \[r=\left( \frac{E}{V}-1 \right)R=\left( \frac{{{l}_{1}}}{{{l}_{2}}}-1 \right)R\]                 \[=\left( \frac{125}{100}-1 \right)\times 2\]                 \[=\left( \frac{5}{4}-1 \right)\times 2=\frac{1}{4}\times =\frac{1}{2}\]                 =0.5\[\Omega \]


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