This is the Multiple Choice Questions (MCQs) in Chapter 9: Alternating Current Basics 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.

### Start Practice Exam Test Questions

1. Which of the following can vary with ac, but not with dc?

- A. Power.
- B. Voltage.
- C. Frequency.
- D. Magnitude.

2. The length of time between a point in one cycle and the same point in the next cycle of an ac wave is the:

- A. Frequency.
- B. Magnitude.
- C. Period.
- D. Polarity.

3. On a spectrum analyzer, a pure ac signal, having just one frequency component, would look like:

- A. A single pip.
- B. A perfect sine wave.
- C. A square wave.
- D. A sawtooth wave.

4. The period of an ac wave is:

- A. The same as the frequency.
- B. Not related to the frequency.
- C. Equal to 1 divided by the frequency.
- D. Equal to the amplitude divided by the frequency.

5. The sixth harmonic of an ac wave whose period is 0.001 second has a frequency of

- A. 0.006 Hz.
- B. 167 Hz.
- C. 7 kHz.
- D. 6 kHz.

6. A degree of phase represents:

- A. 6.28 cycles.
- B. 57.3 cycles.
- C. 1/6.28 cycle.
- D. 1/360 cycle.

7. Two waves have the same frequency but differ in phase by 1/20 cycle. The phase difference in degrees is:

- A. 18.
- B. 20.
- C. 36.
- D. 5.73.

8. A signal has a frequency of 1770 Hz. The angular frequency is:

- A. 1770 radians per second.
- B. 11,120 radians per second.
- C. 282 radians per second.
- D. Impossible to determine from the data given.

9. A triangular wave:

- A. Has a fast rise time and a slow decay time.
- B. Has a slow rise time and a fast decay time.
- C. Has equal rise and decay rates.
- D. Rises and falls abruptly.

10. Three-phase ac:

- A. Has waves that add up to three times the originals.
- B. Has three waves, all of the same magnitude.
- C. Is what you get at a common wall outlet.
- D. Is of interest only to physicists.

11. If two waves have the same frequency and the same amplitude, but opposite phase, the composite wave is:

- A. Twice the amplitude of either wave alone.
- B. Half the amplitude of either wave alone.
- C. A complex waveform, but with the same frequency as the originals.
- D. Zero.

12. If two waves have the same frequency and the same phase, the composite wave:

- A. Has a magnitude equal to the difference between the two originals.
- B. Has a magnitude equal to the sum of the two originals.
- C. Is complex, with the same frequency as the originals.
- D. Is zero.

13. In a 117-V utility circuit, the peak voltage is:

- A. 82.7 V.
- B. 165 V.
- C. 234 V.
- D. 331 V.

14. In a 117-V utility circuit, the pk-pk voltage is:

- A. 82.7 V.
- B. 165 V.
- C. 234 V.
- D. 331 V.

15. In a perfect sine wave, the pk-pk value is:

- A. Half the peak value.
- B. The same as the peak value.
- C. 1.414 times the peak value.
- D. Twice the peak value.

**NOTE: For questions 16 see Fig. 9-15.**

16. If a 45-Vdc battery is connected in series with the 117-V utility mains as shown in Fig. 9-15, the peak voltages will be:

- A. + 210 V and – 120 V.
- B. + 162 V and – 72 V.
- C. + 396 V and – 286 V.
- D. Both equal to 117 V.

17. In the situation of question 16, the pk-pk voltage will be:

- A. 117 V.
- B. 210 V.
- C. 331 V.
- D. 396 V.

18. Which one of the following does *not *affect the power output available from a particular ac generator?

- A. The strength of the magnet.
- B. The number of turns in the coil.
- C. The type of natural energy source used.
- D. The speed of rotation of the coil or magnet.

19. If a 175-V dc source were connected in series with the utility mains from a standard wall outlet, the result would be:

- A. Smooth dc.
- B. Smooth ac.
- C. Ac with one peak greater than the other.
- D. Pulsating dc.

20. An advantage of ac over dc in utility applications is:

- A. Ac is easier to transform from one voltage to another.
- B. Ac is transmitted with lower loss in wires.
- C. Ac can be easily gotten from dc generators.
- D. Ac can be generated with less dangerous by-products.