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JEE Main 2021 (26 Aug, Shift 1) · Combination of Inductors, LR & LC Circuits

Combination of Inductors, LR & LC Circuits question from JEE Main 2021 (26 Aug, Shift 1)

Q25JEE Main 2021 · 26 AUG · SHIFT 1Medium

Combination of Inductors, LR & LC Circuits

An inductor coil stores 64 J of magnetic field energy and dissipates energy at the rate of 640 W when a current of 8A is passed through it. If this coil is joined across an ideal battery, find the time constant of the circuit in seconds:

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Answer: (d)

  1. 12LI2=64⇒L=12864=2 H\frac{1}{2}LI^2 = 64 \Rightarrow L = \frac{128}{64} = 2\text{ H}
  2. I2R=640⇒R=64064=10 ΩI^2 R = 640 \Rightarrow R = \frac{640}{64} = 10\,\Omega
  3. τ=L/R=0.2 s\tau = L/R = 0.2\text{ s}
  4. So the answer is (d).
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