Page 385 - Schaum's Outline of Theory and Problems of Applied Physics

370 ALTERNATING-CURRENT CIRCUITS [CHAP. 29

29.23. (a) Find the resonance frequency f 0 of the circuit of Prob. 29.22. (b) What current will flow in the circuit if it is
connected to a 120-V power source whose frequency is f 0 ?(c) How much power will be dissipated by the circuit?
(d) What must be the minimum rating of the power source in voltamperes?
29.24. A 10- resistor and an 8-µF capacitor are connected in parallel across a 10-V, 1000-Hz power source. Find (a) the
current in each component, (b) the total current, (c) the impedance of the circuit, and (d) the phase angle and power
dissipation of the circuit.

29.25. A 10- resistor and a 2-mH inductor are connected in parallel across a 10-V, 1000-Hz power source. Find (a) the
current in each component, (b) the total current, (c) the impedance of the circuit, and (d) the phase angle and the
total power dissipation of the circuit.
29.26. A 25- resistor, a 40-µF capacitor, and a 40-mH coil are connected in parallel to a 24-V, 100-Hz source. Find (a) the
current in each component, (b) the total current in the circuit, (c) the impedance of the circuit, (d) the phase angle
between current and voltage, and (e) the total power dissipated by the circuit.

29.27. The circuit of Prob. 29.26 is connected to a 24-V, 200-Hz source. Answer the same questions for this case.

29.28. A microphone whose impedance is 20 is to be used with an amplifier whose input impedance is 50,000 . Find
the ratio of turns in the transformer needed to match these two impedances.

Answers to Multiple-Choice Questions

29.1. (d) 29.9. (b)
29.2. (b) 29.10. (c)

29.3. (c) 29.11. (a)

29.4. (c) 29.12. (a)

29.5. (c) 29.13. (b)
29.6. (b) 29.14. (c)

29.7. (b) 29.15. (b)

29.8. (b)

Answers to Supplementary Problems

29.1. R is unchanged, X L is doubled, and X C is halved.

29.2. (a) The minimum value is 0, which can occur only if R = 0 in a circuit in which X L is not equal to X C .
(b) The maximum value is 1, which occurs at resonance when X L = X C .

29.3. (a) 56.6 V (b) 8.5 A (c) Phase angle

29.4. 31.4