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JEE Main202624 January 2026Evening ShiftPhysicsCurrent ElectricityActual

In a meter bridge experiment to determine the value of unknown resistance, first the resistances 2 and 3 are connected in the left and right gaps of the bridge and the null point is obtained at a distance l ~cm from the left. Now when an unknown resistance x is connected in parallel to 3 resistance, the null point is shifted by 10 cm to the right of wire. The value of unknown resistance x is _ _ _ _ .

Correct answer

0

Step-by-step solution

Meter bridge null point condition: R₁ R₂ = l 100-l Initial: R₁ = 2Ω , R₂ = 3Ω , null at l cm 2 3 = l 100-l gives 2(100-l) = 3l , so l = 40 cm When xΩ connected in parallel with 3Ω : R₂' = 3x 3+x Ω New null point at (40+10) = 50 cm from left: 2 R₂' = 50 50 = 1 2(3+x) 3x = 1 gives 6 + 2x = 3x x = 6Ω

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