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JEE Main 2019 (8 Apr, Shift 2) · RL and RC Series Circuits

RL and RC Series Circuits question from JEE Main 2019 (8 Apr, Shift 2)

Q49JEE Main 2019 · 8 APR · SHIFT 2Medium

RL and RC Series Circuits

A circuit connected to an ac source of emf e = e0sin(100t) with t in seconds, gives a phase difference of π\pi/4 between the emf e and current i. Which of the following circuits will exhibit this?

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Answer: (c)

  1. Phase difference π4\frac{\pi}{4} needs reactance X=RX = R; here ω=100 rad/s\omega = 100\text{ rad/s}.
  2. RL: XL=ωL=100×10−3X_L = \omega L = 100 \times 10^{-3} or 100×10−2100 \times 10^{-2}, i.e. 0.10.1 or 1 Ω≠1000 Ω1\ \Omega \ne 1000\ \Omega.
  3. RC with C=10 μFC = 10\ \mu\text{F}: XC=1100×10−5=1000 Ω=RX_C = \frac{1}{100 \times 10^{-5}} = 1000\ \Omega = R. (With 1 μF1\ \mu\text{F}, XC=104 ΩX_C = 10^4\ \Omega.)
  4. So the answer is (c) RC circuit with R=1 kΩR = 1\text{ k}\Omega, C=10 μFC = 10\ \mu\text{F}.
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