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JEE Main 2024 (5 Apr, Shift 1) · Capacitors in DC Circuits & RC

Capacitors in DC Circuits & RC question from JEE Main 2024 (5 Apr, Shift 1)

Q17JEE Main 2024 · 5 APR · SHIFT 1Difficult

Capacitors in DC Circuits & RC

The electric field between the two parallel plates of a capacitor of 1.5 μF1.5\ \mu\text{F} capacitance drops to one third of its initial value in 6.6 μs6.6\ \mu\text{s} when the plates are connected by a thin wire. The resistance of this wire is ________ Ω\Omega. (Given, log⁡e3=1.1\log_e 3=1.1)

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

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Answer: 4

  1. E=qε0A∝qE = \frac{q}{\varepsilon_0 A} \propto q, and on discharge q=q0e−t/RCq = q_0e^{-t/RC}.
  2. e−t/RC=13⇒t=RCln⁡3e^{-t/RC} = \frac{1}{3} \Rightarrow t = RC\ln 3
  3. R=tCln⁡3=6.6×10−61.5×10−6×1.1R = \frac{t}{C\ln 3} = \frac{6.6\times10^{-6}}{1.5\times10^{-6}\times 1.1}
  4. R=4 ΩR = 4\ \Omega
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