Page 383 - Schaum's Outline of Theory and Problems of Applied Physics

368 ALTERNATING-CURRENT CIRCUITS [CHAP. 29

29.9. A circuit that contains a 0.50-µF capacitor, a 20-mH inductor, and an 8.0- resistor has a resonance frequency of
(a) 1.0 kHz (c) 6.3 kHz
(b) 1.6 kHz (d) 16 MHz

29.10. A coil draws a current of 0.250 A and dissipates 10.0 W when it is connected to a 45.0-V ac source. A capacitor is
then connected in series to bring the power factor to 1. The circuit now dissipates
(a) 10.0 W (c) 12.7 W
(b) 11.3 W (d) 14.1 W

29.11. When a 24.0-V, 400-Hz ac source is connected to a series combination of a 5.00-µF capacitor, a 20.0-mH inductor,
and a 40.0- resistor, the current in the circuit is
(a) 0.484 A (c) 0.882 A
(b) 0.600 A (d) 2.25 A
29.12. The phase angle in the circuit of Question 29.11 is

(a) −36 ◦ (c) +36 ◦
(b) −51 ◦ (d) +51 ◦

29.13. The power dissipated in the circuit of Question 29.11 is
(a) 2.5 W (c) 11.6 W
(b) 9.4 W (d) 14.4 W

29.14. The ac source of the circuit of Question 29.11 should have a minimum rating in voltamperes of
(a) 2.5 VA (c) 11.6 VA
(b) 9.4 VA (d) 14.4 VA

29.15. The circuit elements of Question 29.11 are now connected in parallel. When the same ac source is connected to the
combination, the total current the source provides is
(a) 0.424 A (c) 0.983 A
(b) 0.625 A (d) 1.38 A

Supplementary Problems

29.1. The frequency of the alternating emf applied to a series circuit containing resistance, inductance, and capacitance is
doubled. What happens to R, X L , and X C ?

29.2. (a) What is the minimum value the power factor of a circuit can have? Under what circumstances can this occur?
(b) What is the maximum value the power factor can have? Under what circumstances can this occur?

29.3. A voltmeter across an ac circuit reads 40 V, and an ammeter in series with the circuit reads 6 A. (a) What is the
maximum potential difference across the circuit? (b) What is the maximum current in the circuit? (c) What other
information is needed to determine the power consumed in the circuit?

29.4. Find the reactance of 10-mH coil when it is in a 500-Hz circuit.

29.5. The reactance of an inductor is 1000 at 20 Hz. Find its inductance.
29.6. A current of 0.20 A flows through a 0.15-H inductor of negligible resistance that is connected to an 80-V source of
alternating current. What is the frequency of the source?