In a metre bridge experiment, a null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y . - Physics MCQ AIEEE 2004 2026 | ExamTest.live

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In a metre bridge experiment, a null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y . If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4 X against Y ?

Solution & Step-by-step Explanation

For a meter bridge: \frac{R _{1}}{R _{2}} = \frac{l}{100 - l} .Case 1: \frac{X}{Y} = \frac{20}{100 - 20} = \frac{20}{80} = \frac{1}{4} .Case 2: New resistance is 4 X . \frac{4 X}{Y} = \frac{l ^{'}}{100 - l ^{'}} Substitute X / Y = 1/4 : 4 (\frac{1}{4}) = \frac{l ^{'}}{100 - l ^{'}} ⟹ 1 = \frac{l ^{'}}{100 - l ^{'}} 100 - l^{'} = l^{'} ⟹ 2 l^{'} = 100 ⟹ l^{'} = 50 cm

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In a metre bridge experiment, a null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y . If X < Y, then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4 X against Y ?

50 cm

80 cm

40 cm

70 cm

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