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BHU PMT BHU PMT (Screening) Solved Paper-2009

  • question_answer
    In a potentiometer of one metre length, an unknown emf voltage source is balanced at 60 cm length of potentiometer wire, while a 3 V battery is balanced at 45 cm length. Then the emf of the unknown voltage source is

    A)  3V                                         

    B)  2.25V

    C)  4V                                         

    D)  4.5V

    Correct Answer: C

    Solution :

                     Let\[{{l}_{1}}\]and\[{{l}_{2}}\]be the balancing lengths with the cells\[{{E}_{1}}\]and\[{{E}_{2}}\]respectively, than\[{{E}_{1}}=x{{l}_{1}}\]and \[{{E}_{2}}=x{{l}_{2}}\] \[\Rightarrow \]               \[\frac{{{E}_{1}}}{{{E}_{2}}}=\frac{{{l}_{1}}}{{{l}_{2}}}\] Or           \[\frac{{{E}_{1}}}{3}=\frac{60}{45}\] \[\Rightarrow \]               \[E=4V\]


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