This is the Multiple Choice Questions (MCQs) in Chapter 17: Power and Resonance in AC circuits from the book Teach Yourself Electricity and Electronics, 5th edition by Stan Gibilisco. If you are looking for a reviewer in Electronics Engineering this will definitely help you before taking the Board Exam.

### Begin the Test

1. The power in a reactance is:

- A. Radiated power.
- B. True power.
- C. Imaginary power.
- D. Apparent power.

2. Which of the following is *not *an example of true power?

- A. Power that heats a resistor.
- B. Power radiated from an antenna.
- C. Power in a capacitor.
- D. Heat loss in a feed line.

3. The apparent power in a circuit is 100 watts, and the imaginary power is 40 watts. The true power is:

- A. 92 watts.
- B. 100 watts.
- C. 140 watts.
- D. Not determinable from this information.

4. Power factor is equal to:

- A. Apparent power divided by true power.
- B. Imaginary power divided by apparent power.
- C. Imaginary power divided by true power.
- D. True power divided by apparent power.

5. A circuit has a resistance of 300 W and an inductance of 13.5 Î¼H in series at 10.0 MHz. What is the power factor?

- A. 0.334.
- B. 0.999.
- C. 0.595.
- D. It can’t be found from the data given.

6. A series circuit has *Z *= 88.4 Î© with *R *= 50.0 Î© What is PF?

- A. 99.9 percent.
- B. 56.6 percent.
- C. 60.5 percent.
- D. 29.5 percent.

7. A series circuit has *R *= 53.5 Î© and *X *= 75.5 Î©. What is PF?

- A. 70.9 percent.
- B. 81.6 percent.
- C. 57.8 percent.
- D. 63.2 percent.

8. Phase angle is equal to:

- A. Arctan
*Z*/*R*. - B. Arctan
*R*/*Z*. - C. Arctan
*R*/*X*. - D. Arctan
*X*/*R*.

9. A wattmeter shows 220 watts of VA power in a circuit. There is a resistance of 50 Î© in series with a capacitive reactance of −20 Î©. What is the true power?

- A. 237 watts.
- B. 204 watts.
- C. 88.0 watts.
- D. 81.6 watts.

10. A wattmeter shows 57 watts of VA power in a circuit. The resistance is known to be 50 Î©, and the true power is known to be 40 watts. What is the absolute-value impedance?

- A. 50 Î©
- B. 57 Î©
- C. 71 Î©
- D. It can’t be calculated from this data.

11. Which of the following is the most important consideration in a transmission line?

- A. The characteristic impedance.
- B. The resistance.
- C. Minimizing the loss.
- D. The VA power.

12. Which of the following does *not *increase the loss in a transmission line?

- A. Reducing the power output of the source.
- B. Increasing the degree of mismatch between the line and the load.
- C. Reducing the diameter of the line conductors.
- D. Raising the frequency.

13. A problem that standing waves can cause is:

- A. Feed line overheating.
- B. Excessive power loss.
- C. Inaccuracy in power measurement.
- D. All of the above.

14. A coil and capacitor are in series. The inductance is 88 mH and the capacitance is 1000 pF. What is the resonant frequency?

- A. 17 kHz.
- B. 540 Hz.
- C. 17 MHz.
- D. 540 kHz.

15. A coil and capacitor are in parallel, with *L *= 10.0 Î¼H and *C *= 10 pF. What is *f*o?

- A. 15.9 kHz.
- B. 5.04 MHz.
- C. 15.9 MHz.
- D. 50.4 MHz.

16. A series-resonant circuit is to be made for 14.1 MHz. A coil of 13.5 Î¼H is available. What size capacitor is needed?

- A. 0.945 Î¼F.
- B. 9.45 pF.
- C. 94.5 pF.
- D. 945 pF.

17. A parallel-resonant circuit is to be made for 21.3 MHz. A capacitor of 22.0 pF is available. What size coil is needed?

- A. 2.54 mH.
- B. 254 Î¼H.
- C. 25.4 Î¼H.
- D. 2.54 Î¼H.

18. A 1/4-wave line section is made for 21.1 MHz, using cable with a velocity factor of 0.800. How many meters long is it?

- A. 11.1 m.
- B. 3.55 m.
- C. 8.87 m.
- D. 2.84 m.

19. The fourth harmonic of 800 kHz is:

- A. 200 kHz.
- B. 400 kHz.
- C. 3.20 MHz.
- D. 4.00 MHz.

20. How long is a 1/2-wave dipole for 3.60 MHz?

- A. 130 feet.
- B. 1680 feet.
- C. 39.7 feet.
- D. 515 feet.

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