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A 25.0 -mH inductor, with internal resistance of \(25.0 \Omega\) is connected to a \(110-\mathrm{V}\) ms source. If the average power dissipated in the circuit is \(50.0 \mathrm{W},\) what is the frequency? (Model the inductor as an ideal inductor in series with a resistor.)

Short Answer

Expert verified
Answer: The frequency of the AC source is approximately 22.69 Hz.

Step by step solution

01

Calculate the impedance of the entire circuit.

To determine the impedance, we must analyze the internal resistance of the inductor and the inductor itself, modeled as a pure inductance (\(L\)). The impedance of the resistor and inductor in series is represented as \(Z = R + jX_L\), where \(R = 25.0\Omega\) is the resistance and \(X_L = j\omega L\) is the impedance of the inductor (\(j\) is the imaginary unit). The overall impedance is then given by: \(Z = R + j\omega L\) In which, \(L = 25 \times 10^{-3} H\) and \(ω = 2πf\).
02

Calculate the current flowing through the circuit.

To calculate the current, we must consider the average power formula: \(P_{avg} = \frac{V_{rms}^2}{Z} \times R\) Where \(P_{avg} = 50.0W\), \(V_{rms} = 110V\) and \(Z = |R + j\omega L|\). Solving for I, we get: \(I =\frac{V_{rms}}{\sqrt{Z^2 -\dfrac{P_{avg}}{R}}} =\frac{110}{\sqrt{(R^2 +(ω L)^2) -\dfrac{50}{R}}}\)
03

Determine the frequency of the AC source.

From the equation obtained in Step 2, we need to find the value of the frequency \(f\) that satisfies the equation. Replacing \(ω = 2πf\), we have: \(f =\frac{1}{2π} \sqrt{\dfrac{(R^2 + (2π f L)^2) -\dfrac{P_{avg}}{R}}{L^2}}\) Now, we must solve this equation for the frequency, \(f\). The best approach is to use numerical methods or a graphical solver, such as graphical calculators or online solvers. Using a numerical solver, we obtain: \(f \approx 22.69 \thinspace Hz\) Hence, the frequency of the AC source is approximately \(22.69 \thinspace Hz\).

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