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JEE Main 2019 (9 Apr, Shift 1) · Capacitors in DC Circuits & RC

Capacitors in DC Circuits & RC question from JEE Main 2019 (9 Apr, Shift 1)

Q36JEE Main 2019 · 9 APR · SHIFT 1Medium

Capacitors in DC Circuits & RC

Determine the charge on the capacitor in the following circuit:

Figure

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Answer: (a)

  1. Steady state: capacitor branch open. 2+10=12 Ω2+10 = 12\ \Omega in parallel with 4 Ω4\ \Omega gives 3 Ω3\ \Omega; total 6+3=9 Ω6+3 = 9\ \Omega.
  2. I=729=8 AI = \dfrac{72}{9} = 8\text{ A}; voltage across the parallel part =8×3=24 V= 8\times3 = 24\text{ V}.
  3. Current in 2 Ω+10 Ω2\ \Omega + 10\ \Omega: 2412=2 A\dfrac{24}{12} = 2\text{ A}, so V10=20 VV_{10} = 20\text{ V} (capacitor is across it).
  4. Q=10×20=200 μCQ = 10\times20 = 200\ \mu\text{C}, so the answer is (a) 200 μC200\ \mu\text{C}.
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