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JEE Mains · Physics · STD 11 - System of particles and rotational motion
  • JEE Mains 2026
  • Medium
  • MCQ

A LCR series circuit driven with \(E_{rms} = 90\) V at frequency \(f_d = 30\) Hz has resistance \(R = 80\,\Omega\), an inductance with inductive reactance \(X_L = 20.0\,\Omega\) and capacitance with capacitive reactance \(X_C = 80.0\,\Omega\). The power factor of the circuit is _______.

Pick an option to check your answer.
Verified Solution

Answer & Solution

Correct Answer

(A) \(0.8\)

Step-by-step Solution

Detailed explanation

The impedance of the LCR series circuit is given by \(Z = \sqrt{R^2 + (X_C - X_L)^2}\).

Substituting the given values:

\(Z = \sqrt{80^2 + (80 - 20)^2}\)

\(Z = \sqrt{80^2 + 60^2}\)

\(Z = \sqrt{6400 + 3600} = \sqrt{10000} = 100\,\Omega\)

The power factor of the circuit is given by \(\cos \phi = \dfrac{R}{Z}\).

\(\cos \phi = \dfrac{80}{100} = 0.8\)

Answer: \(0.8\)
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