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JEE Main 2010 (AIEEE) · Power, Power Factor & Wattless Current

Power, Power Factor & Wattless Current question from JEE Main 2010 (AIEEE)

Q73JEE Main 2010 · AIEEEDifficult

Power, Power Factor & Wattless Current

In a series LCRLCR circuit R=200 ΩR = 200\ \Omega and the voltage and the frequency of the main supply are 220 V220\text{ V} and 50 Hz50\text{ Hz} respectively. On taking out the capacitance from the circuit the current lags behind the voltage by 30∘.30^\circ. On taking out the inductor from the circuit the current leads the voltage by 30∘.30^\circ. The power dissipated in the LCRLCR circuit is

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Answer: (d)

  1. Without C: tan⁡30∘=XL/R\tan 30^\circ = X_L/R. Without L: tan⁡30∘=XC/R\tan 30^\circ = X_C/R.
  2. So XL=XCX_L = X_C: resonance, Z=RZ = R.
  3. P=V2/R=2202/200=242P = V^2/R = 220^2/200 = 242 W, so the answer is (d).
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