Question:medium

An inductor $20\, mH$, a capacitor $100\, \mu F$ and a resistor $50 \, \Omega$ are connected in series across a source of emf, $V\, = \,10 \,sin\, 314\, t$. The power loss in the circuit is

Updated On: Jun 9, 2026
  • 1.13 W
  • 0.79 W
  • 2.74 W
  • 0.43 W
Show Solution

The Correct Option is B

Solution and Explanation

To determine the power loss in the given RLC circuit with an inductor \(L = 20 \, \text{mH}\), a capacitor \(C = 100 \, \mu \text{F}\), and a resistor \(R = 50 \, \Omega\), connected to a source of emf \(V = 10 \sin 314 t\), let's proceed step-by-step:

  1. Calculate the angular frequency (\( \omega \)):

    The given voltage source is in the form \( V = 10 \sin 314 t \). Comparing it with the standard form \( V = V_0 \sin \omega t \), we identify \(\omega = 314 \, \text{rad/s}\).

  2. Calculate the reactances:
    • Inductive Reactance (\(X_L\)): X_L = \omega L = 314 \times 20 \times 10^{-3} \, \Omega = 6.28 \, \Omega
    • Capacitive Reactance (\(X_C\)): X_C = \frac{1}{\omega C} = \frac{1}{314 \times 100 \times 10^{-6}} \, \Omega = 31.85 \, \Omega
  3. Calculate the impedance (\(Z\)) of the circuit:

    The total impedance \(Z\) of a series RLC circuit is given by:

    Z = \sqrt{R^2 + (X_L - X_C)^2}

    Substitute the values:

    Z = \sqrt{50^2 + (6.28 - 31.85)^2} \, \Omega = \sqrt{50^2 + (-25.57)^2} \, \Omega = \sqrt{2500 + 653.62} \, \Omega = \sqrt{3153.62} \, \Omega \approx 56.15 \, \Omega

  4. Calculate the current (\(I\)) in the circuit:

    The maximum current \(I\) is obtained from the maximum voltage \(V_0 = 10 \, \text{V}\):

    I = \frac{V_0}{Z} = \frac{10}{56.15} \approx 0.178 \, \text{A}

  5. Determine the power loss (\(P\)) in the resistor:

    The average power dissipated in the resistor is given by:

    P = I^2 R = (0.178)^2 \times 50 \approx 0.79 \, \text{W}

Thus, the power loss in the circuit is 0.79 W, which matches option 2. Hence, the correct answer is 0.79 W.

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