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JEE Main 2022 (28 Jun, Shift 2) · Kirchhoff's Laws & Measuring Instruments

Kirchhoff's Laws & Measuring Instruments question from JEE Main 2022 (28 Jun, Shift 2)

Q115JEE Main 2022 · 28 JUN · SHIFT 2Difficult

Kirchhoff's Laws & Measuring Instruments

All resistances in figure are 1 Ω\Omega each. The value of current 'I' is a5\frac{a}{5} A. The value of a is _________.

Figure

Numerical answer type. Work it out, then open the answer.

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Answer: 8

  1. Work from the right: last stage, two 1 Ω1\ \Omega in parallel =0.5 Ω= 0.5\ \Omega.
  2. Next stage: (1+0.5)∥(1+0.5)=0.75 Ω(1 + 0.5) \parallel (1 + 0.5) = 0.75\ \Omega; then (1+0.75)∥(1+0.75)=0.875 Ω(1 + 0.75) \parallel (1 + 0.75) = 0.875\ \Omega.
  3. Total =1+0.875=1.875 Ω= 1 + 0.875 = 1.875\ \Omega
  4. I=31.875=1.6 A=85 AI = \frac{3}{1.875} = 1.6\text{ A} = \frac{8}{5}\text{ A}
  5. Answer: a=8a = 8
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