This is the Part 2 Examination Test (Alternating Current) that includes the succeeding 10 Chapters of 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.

### Topics Included in the Test from Chapter 9 to Chapter 18

**Part 2: Alternating Current**

**MCQs in Alternating-Current Basics**

**MCQs in Inductance****MCQs in Capacitance**

**MCQs in Phase**

**MCQs in Inductive Reactance**

**MCQs in Capacitive Reactance**

**MCQs in Impedance and Admittance****MCQs in RLC and GLC Circuit Analysis**

**MCQs in Transformers and Impedance Matching**

### Start Practice Exam Test Questions

1. A series circuit has a resistance of 100 Ω and a capacitive reactance of -200 Ω. The complex impedance is:

- A. -200 + j100.
- B. 100 + j200.
- C. 200 – j100.
- D. 200 + j100.
- E. 100 – j200.

2. Mutual inductance causes the net value of a set of coils to:

- A. Cancel out, resulting in zero inductance.
- B. Be greater than what it would be with no mutual coupling.
- C. Be less than what it would be with no mutual coupling.
- D. Double.
- E. Vary, depending on the extent and phase of mutual coupling.

**NOTE: For questions 3 see Fig. Test 2-1**

3. Refer to Fig. TEST 2-1. Wave A is:

- A. Leading wave B by 90 degrees.
- B. Lagging wave B by 90 degrees.
- C. Leading wave B by 180 degrees.
- D. Lagging wave B by 135 degrees.
- E. Lagging wave B by 45 degrees.

4. A sine wave has a peak value of 30.0 V. Its rms value is:

- A. 21.2 V.
- B. 30.0 V.
- C. 42.4 V.
- D. 60.0 V.
- E. 90.0 V.

5. Four capacitors are connected in parallel. Their values are 100 pF each. The net capacitance is:

- A. 25 pF.
- B. 50 pF.
- C. 100 pF.
- D. 200 pF.
- E. 400 pF.

6. A transformer has a primary-to-secondary turns ratio of exactly 8.88:1. The input voltage is 234 V rms. The output voltage is:

- A. 2.08 kV rms.
- B. 18.5 kV rms.
- C. 2.97 V rms.
- D. 26.4 V rms.
- E. 20.8 V rms.

7. In a series RL circuit, as the resistance becomes small compared with the reactance, the angle of lag approaches:

- A. 0 degrees.
- B. 45 degrees.
- C. 90 degrees.
- D. 180 degrees.
- E. 360 degrees.

8. A transmission line carries 3.50 A of ac current and 150 V ac. The *true power *in the line is:

- A. 525 W.
- B. 42.9 W.
- C. 1.84 W.
- D. Meaningless; true power is dissipated, not transmitted.
- E. Variable, depending on standing wave effects.

9. In a parallel configuration, susceptances:

- A. Simply add up.
- B. Add like capacitances in series.
- C. Add like inductances in parallel.
- D. Must be changed to reactances before you can work with them.
- E. Cancel out.

10. A wave has a frequency of 200 kHz. How many degrees of phase change occur in a microsecond (a millionth of a second)?

- A. 180 degrees.
- B. 144 degrees.
- C. 120 degrees.
- D. 90 degrees.
- E. 72 degrees.

11. At a frequency of 2.55 MHz, a 330-pF capacitor has a reactance of:

- A. −5.28 Ω
- B. −0.00528 Ω
- C. −189 Ω
- D. −18.9k Ω
- E. −0.000189 Ω

12. A transformer has a step-up turns ratio of 1:3.16. The output impedance is 499Ω purely resistive. The input impedance is:

- A. 50.0 Ω
- B. 158 Ω
- C. 1.58k Ω
- D. 4.98k Ω
- E. Not determinable from the data given.

13. A complex impedance is represented by 34 − *j*23. The absolute-value impedance is:

- A. 34 Ω
- B. 11 Ω
- C. -23 Ω
- D. 41 Ω
- E. 57 Ω

14. A coil has an inductance of 750 μH. The inductive reactance at 100 kHz is:

- A. 75.0 Ω
- B. 75.0 k Ω
- C. 471 Ω
- D. 47.1 k Ω
- E. 212 Ω

15. Two waves are 180 degrees out of phase. This is a difference of:

- A. 1/8 cycle.
- B. 1/4 cycle.
- C. 1/2 cycle.
- D. A full cycle.
- E. Two full cycles.

16. If *R *denotes resistance and *Z *denotes absolute-value impedance, then *R*/*Z *is the:

- A. True power.
- B. Imaginary power.
- C. Apparent power.
- D. Absolute-value power.
- E. Power factor.

17. Two complex impedances are in series. One is 30 + *j*50 and the other is 50 − *j*30. The net impedance is:

- A. 80 +
*j*80. - B. 20 +
*j*20. - C. 20 –
*j*20. - D. –20 +
*j*20. - E. 80 +
*j*20.

18. Two inductors, having values of 140 μH and 1.50 mH, are connected in series. The net inductance is:

- A. 141.5 μH.
- B. 1.64 μH.
- C. 0.1415 mH.
- D. 1.64 mH.
- E. 0.164 mH.

19. Which of the following types of capacitor is polarized?

- A. Mica.
- B. Paper.
- C. Electrolytic.
- D. Air variable.
- E. Ceramic.

20. A toroidal-core coil:

- A. Has lower inductance than an air-core coil with the same number of turns.
- B. Is essentially self-shielding.
- C. Works well as a loopstick antenna.
- D. Is ideal as a transmission-line transformer.
- E. Cannot be used at frequencies below about 10 MHz.

21. The efficiency of a generator:

- A. Depends on the driving power source.
- B. Is equal to output power divided by driving power.
- C. Depends on the nature of the load.
- D. Is equal to driving voltage divided by output voltage.
- E. Is equal to driving current divided by output current.

22. Admittance is:

- A. The reciprocal of reactance.
- B. The reciprocal of resistance.
- C. A measure of the opposition a circuit offers to ac.
- D. A measure of the ease with which a circuit passes ac.
- E. Another expression for absolute-value impedance.

23. The absolute-value impedance *Z *of a parallel RLC circuit, where *R *is the resistance and *X *is the net reactance, is found according to the formula:

- A.
*Z*=*R +**X.* - B.
*Z*2 =*R*2 +*X*2*.* - C.
*Z*2=*RX*/ (*R*2 +*X*2). - D. Z = 1/(
*R*2 +*X*2). - E.
*Z*=*R*2*X*2*/(R*+*X*).

24. Complex numbers are used to represent impedance because:

- A. Reactance cannot store power.
- B. Reactance isn’t a real physical thing.
- C. They provide a way to represent what happens in resistance-reactance circuits.
- D. Engineers like to work with sophisticated mathematics.
- E. No! Complex numbers aren’t used to represent impedance.

25. Which of the following does *not *affect the capacitance of a capacitor?

- A. The mutual surface area of the plates.
- B. The dielectric constant of the material between the plates (within reason).
- C. The spacing between the plates (within reason).
- D. The amount of overlap between plates.
- E. The frequency (within reason).

26. The zero-degree phase point in an ac sine wave is usually considered to be the instant at which the amplitude is:

- A. Zero and negative-going.
- B. At its negative peak.
- C. Zero and positive-going.
- D. At its positive peak.
- E. Any value; it doesn’t matter.

27. The inductance of a coil can be continuously varied by:

- A. Varying the frequency.
- B. Varying the net core permeability.
- C. Varying the current in the coil.
- D. Varying the wavelength.
- E. Varying the voltage across the coil.

28. Power factor is defined as the ratio of:

- A. True power to VA power.
- B. True power to imaginary power.
- C. Imaginary power to VA power.
- D. Imaginary power to true power.
- E. VA power to true power.

29. A 50 Ω feed line needs to be matched to an antenna with a purely resistive impedance of 200 Ω A quarter-wave matching section should have:

- A.
*Z*o = 150 Ω - B.
*Z*o = 250 Ω - C.
*Z*o = 125 Ω - D.
*Z*o = 133 Ω - E.
*Z*o = 100 Ω

30. The vector 40 + *j*30 represents:

- A. 40 Ω resistance and 30 μH inductance.
- B. 40 uH inductance and 30 Ω resistance.
- C. 40 Ω resistance and 30 Ω inductive reactance.
- D. 40 Ω inductive reactance and 30 Ω resistance.
- E. 40 uH inductive reactance and 30 Ω resistance.

31. In a series RC circuit, where, *R *= 300 Ω and *X*C = −30 Ω:

- A. The current leads the voltage by a few degrees.
- B. The current leads the voltage by almost 90 degrees.
- C. The voltage leads the current by a few degrees.
- D. The voltage leads the current by almost 90 degrees.
- E. The voltage leads the current by 90 degrees.

32. In a step-down transformer:

- A. The primary voltage is greater than the secondary voltage.
- B. The primary impedance is less than the secondary impedance.
- C. The secondary voltage is greater than the primary voltage.
- D. The output frequency is higher than the input frequency.
- E. The output frequency is lower than the input frequency.

33. A capacitor of 470 pF is in parallel with an inductor of 4.44 μH. What is the resonant frequency?

- A. 3.49 MHz.
- B. 3.49 kHz.
- C. 13.0 MHz.
- D. 13.0 GHz.
- E. Not determinable from the data given.

34. A sine wave contains energy at:

- A. Just one frequency.
- B. A frequency and its even harmonics.
- C. A frequency and its odd harmonics.
- D. A frequency and all its harmonics.
- E. A frequency and its second harmonic only.

35. Inductive susceptance is:

- A. The reciprocal of inductance.
- B. Negative imaginary.
- C. Equal to capacitive reactance.
- D. The reciprocal of capacitive susceptance.
- E. A measure of the opposition a coil offers to ac.

36. The rate of change (derivative) of a sine wave is itself a wave that:

- A. Is in phase with the original wave.
- B. Is 180 degrees out of phase with the original wave.
- C. Leads the original wave by 45 degrees of phase.
- D. Lags the original wave by 90 degrees of phase.
- E. Leads the original wave by 90 degrees of phase.

37. True power is equal to:

- A. VA power plus imaginary power.
- B. Imaginary power minus VA power.
- C. Vector difference of VA and reactive power.
- D. VA power; the two are the same thing.
- E. 0.707 times the VA power.

38. Three capacitors are connected in series. Their values are 47 μF, 68 μF, and 100 μF. The total capacitance is:

- A. 215 μF.
- B. Between 68 μF and 100 μF.
- C. Between 47 μF and 68 μF.
- D. 22 μF.
- E. Not determinable from the data given.

39. The reactance of a section of transmission line depends on all of the following *except*:

- A. The velocity factor of the line.
- B. The length of the section.
- C. The current in the line.
- D. The frequency.
- E. The wavelength.

40. When confronted with a parallel RLC circuit and you need to find the complex impedance:

- A. Just add the resistance and reactance to get
*R +**jX*. - B. Find the net conductance and susceptance, then convert to resistance and reactance, and add these to get
*R + jX.* - C. Find the net conductance and susceptance, and just add these together to get
*R +**jX*. - D. Rearrange the components so they’re in series, and find the complex impedance of that circuit.
- E. Subtract reactance from resistance to get
*R*−*jX.*

**NOTE: For questions 41 see Fig. Test 2-2**

41. The illustration in Fig. Test 2-2 shows a vector *R + **jX *representing:

- A.
*XC*= 60 Ω and*R*= 25 Ω - B.
*X*L = 60 Ω and*R*= 25 Ω - C.
*X*L = 60 μH and*R*= 25 Ω - D.
*C*= 60 μF and*R*= 25 Ω - E.
*L*= 60 μH and*R*= 25 Ω

42. If two sine waves have the same frequency and the same amplitude, but they cancel out, the phase difference is:

- A. 45 degrees.
- B. 90 degrees.
- C. 180 degrees.
- D. 270 degrees.
- E. 360 degrees.

43. A series circuit has a resistance of 50 Ω and a capacitive reactance of −37 Ω.* *The phase angle is:

- A. 37 degrees.
- B. 53 degrees.
- C. −37 degrees.
- D. −53 degrees.
- E. Not determinable from the data given.

44. A 200 Ω resistor is in series with a coil and capacitor; *X*L = 200 Ω and *X*C = −100 Ω. The complex impedance is:

- A. 200 −
*j*100. - B. 200 −
*j*200. - C. 200 +
*j*100. - D. 200 +
*j*200. - E. Not determinable from the data given.

45. The characteristic impedance of a transmission line:

- A. Is negative imaginary.
- B. Is positive imaginary.
- C. Depends on the frequency.
- D. Depends on the construction of the line.
- E. Depends on the length of the line.

46. The period of a wave is 2 X 10−8 second. The frequency is:

- A. 2 X 108 Hz.
- B. 20 MHz.
- C. 50 kHz.
- D. 50 MHz.
- E. 500 MHz.

47. A series circuit has a resistance of 600 Ω and a capacitance of 220 pF. The phase angle is:

- A. −20 degrees.
- B. 20 degrees.
- C. −70 degrees.
- D. 70 degrees.
- E. Not determinable from the data given.

48. A capacitor with a negative temperature coefficient:

- A. Works less well as the temperature increases.
- B. Works better as the temperature increases.
- C. Heats up as its value is made larger.
- D. Cools down as its value is made larger.
- E. Has increasing capacitance as temperature goes down.

49. Three coils are connected in parallel. Each has an inductance of 300μH. There is no mutual inductance. The net inductance is:

- A. 100 μH.
- B. 300 μH.
- C. 900 μH.
- D. 17.3 μH.
- E. 173 μH.

50. An inductor shows 100 Ω of reactance at 30.0 MHz. What is its inductance?

- A. 0.531 μH.
- B. 18.8 mH.
- C. 531 μH.
- D. 18.8 μH.
- E. It can’t be found from the data given.