 Capacitive Reactance – Gibilisco MCQs in Electronics

(Last Updated On: December 8, 2017) 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 + j323.
• B. 323 + j8.02.
• C. 8.02 – j323.
• D. 323 – j8.02.

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.