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JEE Main 2019 (8 Apr, Shift 1) · Kirchhoff's Laws & Measuring Instruments

Kirchhoff's Laws & Measuring Instruments question from JEE Main 2019 (8 Apr, Shift 1)

Q159JEE Main 2019 · 8 APR · SHIFT 1Medium

Kirchhoff's Laws & Measuring Instruments

For the circuit shown, with R1 = 1.0 Ω\Omega, R2 = 2.0 Ω\Omega, E1 = 2 V and E2 = E3 = 4 V, the potential difference between the points 'a' and 'b' is approximately (in V):

Figure

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Answer: (a)

  1. Three branches lie between a and b: (E1=2E_1 = 2, 2R1=2 Ω2R_1 = 2\ \Omega), (E2=4E_2 = 4, R2=2 ΩR_2 = 2\ \Omega), (E3=4E_3 = 4, 2R1=2 Ω2R_1 = 2\ \Omega), all with + towards a.
  2. Parallel-cell (Millman) formula: Vab=∑E/r∑1/rV_{ab} = \frac{\sum E/r}{\sum 1/r}
  3. Vab=2/2+4/2+4/21/2+1/2+1/2=51.5≈3.3 VV_{ab} = \frac{2/2 + 4/2 + 4/2}{1/2 + 1/2 + 1/2} = \frac{5}{1.5} \approx 3.3\text{ V}
  4. So the answer is (a) 3.3.
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