Uncategorized

Teach Yourself Electricity and Electronics Examination Part 2

Multiple choice questions in Teach Yourself Electricity and Electronics Examination Part 2

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
Chapter 10: MCQs in Inductance
Chapter 12: MCQs in Phase

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

Gibilisco MCQs image for test2 Q3

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 − j23. 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 + j50 and the other is 50 − j30. The net impedance is:

  • A. 80 + j80.
  • B. 20 + j20.
  • C. 20 – j20.
  • D. –20 + j20.
  • E. 80 + j20.

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. Z2 = R2 + X2.
  • C. Z2= RX / (R2 + X2).
  • D. Z = 1/(R2 + X2).
  • E. Z = R2X2/(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. Zo = 150 Ω
  • B. Zo = 250 Ω
  • C. Zo = 125 Ω
  • D. Zo = 133 Ω
  • E. Zo = 100 Ω

30. The vector 40 + j30 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 XC = −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

Gibilisco MCQs image for test2 Q41

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

  • A. XC = 60 Ω and R = 25 Ω
  • B. XL = 60 Ω and R = 25 Ω
  • C. XL = 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; XL = 200 Ω and XC = −100 Ω. The complex impedance is:

  • A. 200 − j100.
  • B. 200 − j200.
  • C. 200 +  j100.
  • D. 200 + j200.
  • 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.

Complete List of Multiple Choice Questions from this Book

Check your work.

Leave a Reply

Your email address will not be published. Required fields are marked *