This is the Multiple Choice Questions (MCQs) in Chapter 14: Capacitive Reactance 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. As the size of the plates in a capacitor increases, all other things being equal:

- A. The value of
*XC*increases negatively. - B. The value of
*XC*decreases negatively. - C. The value of
*XC*does not change. - D. You can’t say what happens to
*XC*without more data.

2. If the dielectric material between the plates of a capacitor is changed, all other things being equal:

- A. The value of
*XC*increases negatively. - B. The value of
*XC*decreases negatively. - C. The value of
*XC*does not change. - D. You can’t say what happens to
*XC*without more data.

3. As the frequency of a wave gets lower, all other things being equal, the value of *XC *for a capacitor:

- A. Increases negatively.
- B. Decreases negatively.
- C. Does not change.
- D. Depends on the current.

4. A capacitor has a value of 330 pF. What is its capacitive reactance at a frequency of 800 kHz?

- A. -1.66 Ω.
- B. -0.00166 Ω.
- C. -603 Ω.
- D. -603 K Ω.

5. A capacitor has a reactance of -4.50 Ω at 377 Hz. What is its capacitance?

- A. 9.39 μF.
- B. 93.9 μF.
- C. 7.42 μF.
- D. 74.2 μF.

6. A capacitor has a value of 47 μF. Its reactance is -47 Ω. What is the

frequency?

- A. 72 Hz.
- B. 7.2 MHz.
- C. 0.000072 Hz.
- D. 7.2 Hz.

7. A capacitor has *XC *= -8800 Ω at *f *= 830 kHz. What is *C*?

- A. 2.18 μF.
- B. 21.8 pF.
- C. 0.00218 μF.
- D. 2.18 pF.

8. A capacitor has *C *= 166 pF at *f *= 400 kHz. What is *XC*?

- A. -2.4 K Ω.
- B. -2.4 Ω.
- C. -2.4 x 10-6 Ω.
- D. -2.4 M Ω.

9. A capacitor has *C *= 4700 μF and *XC* = -33 Ω. What is *f*?

- A. 1.0 Hz.
- B. 10 Hz.
- C. 1.0 kHz.
- D. 10 kHz.

10. Each point in the RC plane:

- A. Corresponds to a unique inductance.
- B. Corresponds to a unique capacitance.
- C. Corresponds to a unique combination of resistance and capacitance.
- D. Corresponds to a unique combination of resistance and reactance.

11 If *R *increases in an RC circuit, but *XC *is always zero, then the vector in the RC plane will:

- A. Rotate clockwise.
- B. Rotate counterclockwise.
- C. Always point straight towards the right.
- D. Always point straight down.

12. If the resistance *R *increases in an RC circuit, but the capacitance and the frequency are nonzero and constant, then the vector in the RC plane will:

- A. Get longer and rotate clockwise.
- B. Get longer and rotate counterclockwise.
- C. Get shorter and rotate clockwise.
- D. Get shorter and rotate counterclockwise.

13. Each impedance *R *– *jXC*:

- A. Represents a unique combination of resistance and capacitance.
- B. Represents a unique combination of resistance and reactance.
- C. Represents a unique combination of resistance and frequency.
- D. All of the above.

14. In an RC circuit, as the ratio of capacitive reactance to resistance, –*XC*/*R*, gets closer to zero, the phase angle:

- A. Gets closer to -90 degrees.
- B. Gets closer to 0 degrees.
- C. Stays the same.
- D. Cannot be found.

15. In a purely resistive circuit, the phase angle is:

- A. Increasing.
- B. Decreasing.
- C. 0 degrees.
- D. -90 degrees.

16. If the ratio of *XC*/*R *is 1, the phase angle is:

- A. 0 degrees.
- B. -45 degrees.
- C. -90 degrees.
- D. Impossible to find; there’s not enough data given.

**NOTE: For questions 17 – 18 see Fig.14-13.**

17. In Fig. 14-13, the impedance shown is:

- A. 8.02 +
*j*323. - B. 323 +
*j*8.02. - C. 8.02 –
*j*323. - D. 323 –
*j*8.02.

18. In Fig. 14-13, note that the *R *and *XC *scale divisions are not the same size. The phase angle is

- A. 1.42 degrees.
- B. About -60 degrees, from the looks of it.
- C. -58.9 degrees.
- D. -88.6 degrees.

19. An RC circuit consists of a 150-pF capacitor and a 330 Ω resistor in series. What is the phase angle at a frequency of 1.34 MHz?

- A. –67.4 degrees.
- B. –22.6 degrees.
- C. –24.4 degrees.
- D. –65.6 degrees.

20. An RC circuit has a capacitance of 0.015 μF. The resistance is 52 Ω. What is the phase angle at 90 kHz?

- A. –24 degrees.
- B. –0.017 degrees.
- C. –66 degrees.
- D. None of the above.