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10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    There is a fixed potential difference between the two ends of a potentiometer. Two cells are connected in series in such a way that in one arrangement they help each other where as in the second arrangement they oppose each other The balance point for these two combinations is obtained at 120 cm and 60 cm length respectively. The ratio of the emf of the cell is        

    A)  2 : 1            

    B)                        3:1          

    C)  1:1                        

    D)         4:1           

    Correct Answer: B

    Solution :

                       \[\frac{{{E}_{1}}+{{E}_{2}}}{{{E}_{1}}-{{E}_{2}}}=\frac{120}{60}=2:1\] Applying componendo and dividendo,                 \[\frac{{{E}_{1}}}{{{E}_{2}}}=\frac{2+1}{2-1}=\frac{3}{1}\]


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