For a cell of emf 2 V, a balance is obtained for 50 cm of the potentiometer wire. If the cell is shunted by a 2 n resistor and the balance is obtained across 40 cm of the wire, then the internal resistance of the cell is:
Using the potentiometer principle:
E∝L
Initially, the balance length is L₁ = 50 cm. When the cell is shunted by Rₛ = 2 Ω, the new balance length is L₂ = 40 cm.
Class 12th Science Physics NCERT MCQ Questions
NCERT Books MCQ Questions Session 2024-2025.
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Using the meter bridge formula:
R/S = L/100 – L
Given R = 2Ω and
L = 40 cm:
2/S = 40/60
S = 2 × 60/40 = 3Ω
Answer: (b) 0.5 Ω
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