Two known resistances are connected in two gaps of a meter bridge. The null point is obtained at 20 cm from zero end. A resistance of 15Ω is connected in series with the smaller of the two. The null p

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Two known resistances are connected in two gaps of a meter bridge. The null point is obtained at 20 cm from zero end. A resistance of 15Ω is connected in series with the smaller of the two. The null point shifts to 40 cm . The smaller resistances is

TestHub · Accepted Answer

Given l = 20 cm l ′ = 40 cm Using R 2 ​ R 1 ​ ​ = 100 − l l ​ ​ ∴ R 2 ​ R 1 ​ ​ = 100 − 20 20 ​ ⇒ R 2 ​ = 4 R 1 ​ ​ Again using R 2 ​ R 1 ​ ​ = 100 − l ′ l ′ ​ , where l ′ = 40 cm , R 1 ​ = R ′ 1 ​ + 15 and ​ R 2 ′ ​ = R 2 ​ = 4 R 1 ​ ∴ 4 R 1 ​ R 1 ​ + 15 ​ = 100 − 40 40 ​ ⇒ R 1 ​ = 9Ω ​

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