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For the circuit shown, with R₁=1.0 Ω, R₂=2.0 Ω, E₁=2 V and E₂=E₃=4 V, the potential difference between the points a and b is approximately (in V) [Figure: point a on the top wire, point b on the bottom wire. Left branch between a and b: a, resistor R₁ along the top to the left side, cell E₁ down the left side, resistor R₁ along the bottom to b. Middle branch: a, resistor R₂, cell E₂, b. Right branch: a, resistor R₁ along the top to the right side, cell E₃ and resistor R₁ down the right side, bottom wire to b. All three cells have their positive terminals toward the top wire.]

Asked in JEE Main 8th April 1st Shift 2019 · Kirchhoff's laws in networks

Figure: Kirchhoff's laws in networks
Answer: (4) 3.3

Step-by-step solution

Three branches join a and b, each an emf in series with 2 Ω.

Left: E₁=2 V, R₁+R₁=2 Ω. Middle: E₂=4 V, R₂=2 Ω. Right: E₃=4 V, R₁+R₁=2 Ω.

Parallel emfs: V_ab=(Σ Eᵢ/rᵢ)/(Σ 1/rᵢ)=(1+2+2)/(0.5+0.5+0.5).

V_ab=5/(1.5)=3.3 V.

Why the other options are wrong

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