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JEE Main 2020 (2 Sep, Shift 2) · RL and RC Series Circuits

RL and RC Series Circuits question from JEE Main 2020 (2 Sep, Shift 2)

Q47JEE Main 2020 · 2 SEP · SHIFT 2Difficult

RL and RC Series Circuits

An inductance coil has an impedance of 100 Ω\Omega. When an AC signal of frequency 1000 Hz is applied to the coil, the applied voltage leads the current by 45°. The self-inductance of the coil is

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Answer: (d)

  1. Voltage leads current by 45∘45^\circ: tan⁡45∘=XLR=1⇒XL=R\tan 45^\circ = \frac{X_L}{R} = 1 \Rightarrow X_L = R.
  2. Z=R2+XL2=2 XL=100 Ω⇒XL=70.7 ΩZ = \sqrt{R^2 + X_L^2} = \sqrt{2}\,X_L = 100\ \Omega \Rightarrow X_L = 70.7\ \Omega
  3. L=XL2πf=70.72π×1000≈1.1×10−2 HL = \frac{X_L}{2\pi f} = \frac{70.7}{2\pi \times 1000} \approx 1.1 \times 10^{-2}\ \text{H}
  4. So the answer is (d) 1.1×10−21.1 \times 10^{-2} H.
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