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10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    In a meter bridge, a standard resistor of R ohm is connected in the left gap and two wires A and B are connected one after the other in the right gap. The balancing length measured from the left is 50 cm for either of them. If the two wires are connected is series and put in the right gap, the balancing length measured from the left would be (in cm)

    A)  25  

    B) \[~\text{33}\text{.3}\]

    C)  \[\text{66}\text{.7}\]

    D)  75

    Correct Answer: A

    Solution :

     Let the resistance of wire \[A\] be \[a\] and that of wire \[B\] and\[b\], then                 \[\frac{R}{50}=\frac{a}{100-50}\],             \[i.e.\]  \[a=R\] Also       \[\frac{R}{50}=\frac{b}{100-50},\]             \[i.e.\]  \[b=R\] So              \[a=b\] When both are connected in series,\[\frac{R}{l}=\frac{2a}{100-i}\]or\[100-l=2i\]or\[i=\frac{100}{3}\]


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