/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 79 An ac series circuit containing ... [FREE SOLUTION] | 91Ó°ÊÓ

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An ac series circuit containing a capacitor, inductor, and resistance is found to have a current of amplitude \(0.50 \mathrm{A}\) for a source voltage of amplitude \(10.0 \mathrm{V}\) at an angular frequency of $200.0 \mathrm{rad} / \mathrm{s} .\( The total resistance in the circuit is \)15.0 \Omega$ (a) What are the power factor and the phase angle for the circuit? (b) Can you determine whether the current leads or lags the source voltage? Explain.

Short Answer

Expert verified
Based on the given information and calculations for this circuit: a) The power factor is 0.75, and the phase angle between the voltage and current is 41.4 degrees. b) It is not possible to determine whether the current leads or lags the source voltage without more information about the inductor and capacitor values in the circuit.

Step by step solution

01

Calculate impedance amplitude

The Impedance (Z) of the circuit can be found using the given amplitude of Voltage(V) and Current(I) using, \(Z =\frac{V}{I}\). So, plug in the given values to get the Impedance (Z) of the circuit. $$Z = \frac{10.0 V}{0.50 A} = 20.0 \,\Omega !$$
02

Calculate reactance amplitude

Next, we find the amplitude of the reactance (X). We are given the resistance (R) in the circuit and we have calculated impedance (Z), so we can use the following formula to find the reactance (X): $$X = \sqrt{Z^2 - R^2}$$ where X is the reactance, Z is impedance, and R is resistance. $$X = \sqrt{(20.0 \, \Omega)^2 - (15.0 \, \Omega)^2} = \sqrt{625} \, \Omega$$ $$X = 25.0 \, \Omega$$
03

Calculate the power factor

Now that we have the impedance (Z) and resistance (R), we can calculate the power factor (PF) of the circuit using the following formula: $$PF = \frac{R}{Z}$$ $$PF = \frac{15.0 \, \Omega}{20.0 \, \Omega} = 0.75$$
04

Calculate the phase angle

Using the power factor, we can calculate the phase angle (θ) between the voltage and current using: $$\cos{\theta} = PF$$ $$\theta = \arccos{(PF)}$$ $$\theta = \arccos{(0.75)} = 41.4°$$
05

Determine if current leads or lags the source voltage

The circuit contains a resistor, inductor, and capacitor. In an inductor, the current lags the voltage, and in a capacitor, the current leads the voltage. Since we are not told the values of the inductor (L) and capacitor (C), we cannot determine the net effect in this case. However, if the net effect was reactive (inductive or capacitive), the magnitude of the phase angle would have been exactly 90°. But the phase angle is 41.4° which is not exactly 90°. So, there must be some complex combination of inductor and capacitor effects that lead to a net phase angle of 41.4°. Hence, we cannot determine whether the current leads or lags the source voltage without more information. In conclusion: a) The power factor for the circuit is 0.75, and the phase angle is 41.4°. b) We cannot determine whether the current leads or lags the source voltage without more information on the inductor and capacitor values.

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Most popular questions from this chapter

A \(150-\Omega\) resistor is in series with a \(0.75-\mathrm{H}\) inductor in an ac circuit. The rms voltages across the two are the same. (a) What is the frequency? (b) Would each of the rms voltages be half of the rms voltage of the source? If not, what fraction of the source voltage are they? (In other words, \(V_{R} / \ell_{m}=V_{L} / \mathcal{E}_{m}=?\) ) (c) What is the phase angle between the source voltage and the current? Which leads? (d) What is the impedance of the circuit?
The voltage across an inductor and the current through the inductor are related by \(v_{\mathrm{L}}=L \Delta i / \Delta t .\) Suppose that $i(t)=I \sin \omega t .\( (a) Write an expression for \)v_{\mathrm{L}}(t) .$ [Hint: Use one of the relationships of Eq. \((20-7) .]\) (b) From your expression for \(v_{\mathrm{L}}(t),\) show that the reactance of the inductor is \(X_{\mathrm{L}}=\omega L_{\mathrm{r}}\) (c) Sketch graphs of \(i(t)\) and \(v_{\mathrm{L}}(t)\) on the same axes. What is the phase difference? Which one leads?
A variable capacitor with negligible resistance is connected to an ac voltage source. How does the current in the circuit change if the capacitance is increased by a factor of 3.0 and the driving frequency is increased by a factor of \(2.0 ?\)
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Make a figure analogous to Fig. 21.4 for an ideal inductor in an ac circuit. Start by assuming that the voltage across an ideal inductor is \(v_{\mathrm{L}}(t)=V_{\mathrm{L}}\) sin \(\omega t .\) Make a graph showing one cycle of \(v_{\mathrm{L}}(t)\) and \(i(t)\) on the same axes. Then, at each of the times \(t=0, \frac{1}{8} T, \frac{2}{8} T, \ldots, T,\) indicate the direction of the current (or that it is zero), whether the current is increasing, decreasing, or (instantaneously) not changing, and the direction of the induced emf in the inductor (or that it is zero).
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