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Figure 9.90

← Back to Fundamentals of Electric Circuits Overview 9.85 The ac bridge circuit of Fig. 9.85 is called a Wien bridge. It is used for measuring the frequency of a source. Show that when the bridge is balanced,

________ R2R4C2C4

measurements are taken at 60 Hz when the circuit operates in the steady state:

∣Vs∣=145 V,∣V1∣=50 V,∣Vo∣=110 V|\mathbf{V}_s| = 145 \text{ V}, \qquad |\mathbf{V}_1| = 50 \text{ V}, \qquad |\mathbf{V}_o| = 110 \text{ V}

Use these measurements to determine the values of L and R.

Figure 9.90

For Prob. 9.90.

9.91 Figure 9.91 shows a series combination of an inductance and a resistance. If it is desired to connect a capacitor in parallel with the series combination such that the net impedance is resistive at 10 kHz, what is the required value of C?

Figure 9.91 For Prob. 9.91.

  • 9.92 A transmission line has a series impedance of Z = 100⧸ 75° Ω and a shunt admittance of Y = 450⧸ 48° μS. Find: (a) the characteristic impedance Zo = √ _____ Z∕Y , (b) the propagation constant γ = √ ___ ZY .
  • 9.93 A power transmission system is modeled as shown in Fig. 9.92. Given the source voltage and circuit elements
Vs = 115⧸ 0° V,source impedance
Zs = (1 + j0.5) Ω,line impedance
Zt = (0.4 + j0.3) Ω,and load impedance
ZL = (23.2 + j18.9) Ω,find the load current IL.

Figure 9.92 For Prob. 9.93.

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