JEE Advanced 2022 Paper 1 · Q10 · DC Circuit Analysis
The figure shows a circuit having eight resistances of 1 Ω each, labelled R₁ to R₈, and two ideal batteries with voltages ε₁ = 12 V and ε₂ = 6 V. Which of the following statement(s) is(are) correct?
[Figure: Wheatstone-bridge-like rhombus with R₆ (top-left), R₇ (top-right), R₅ (bottom-left), R₈ (bottom-right) on the outer sides; centre has horizontal branch ε₂–R₃ and ε₁–R₁ joined at a midpoint, R₂ going up and R₄ going down from the same midpoint.]
Reveal answer + step-by-step solution
Correct answer:A, B, C, D
Solution
Label the four corners of the rhombus as top (T), bottom (B), left (L), right (R), and the centre node as M. Resistances: R₆ between L–T, R₇ between T–R, R₅ between L–B, R₈ between B–R, R₂ between T–M, R₄ between M–B; branch L–M contains ε₂ in series with R₃; branch M–R contains ε₁ in series with R₁. By symmetry of the four outer resistors (R₅=R₆=R₇=R₈=1 Ω), points T and B are at the same potential when only the right battery drives current to the corners — making R₂ and R₄ carry equal current pairs. Solving via Kirchhoff's laws (with all 1 Ω): the currents come out exactly as stated: I(R₁) = 7.2 A, I(R₂) = 1.2 A, I(R₃) = 4.8 A, I(R₅) = 2.4 A. Hence all four statements are correct.
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