In the meterbridge experimental set up, shown the null point `D` is obtained at a distance of `40 cm` from end A of the meter bridge wire if a resistance of `10 Omega` is connected in series with `R_(1)`, null point is obtained at `AD = 30 cm`

Answer

`8 Omega`

Explanation

Case (i) `(R_(1))/(R_(2)) = (40)/(60) = (2)/(3) or R_(1) = (2)/(3) R_(2)`….(i)
Case (ii) , `(R_(1) + 10)/(R_(2)) = (60)/(40) = (2)/(3)`
or `2R_(1) + 20= 3R_(2)`
or `2 xx (2)/(3) R_(2) + 20 = 3R_(2) or 4R_(2) + 60 = 9 R_(2)`
or `R_(2) = 12 Omega` from (i) `R_(1) = (2)/(3) xx 12 = 8 Omega`