 # NEETS Module 02 Assignment 1: Concepts of Alternating Current

(Last Updated On: December 8, 2017)

This is the Textbook Assignment: Chapter 1, “Concepts of Alternating Current” from the Module 2 — Introduction to Alternating Current and Transformers in Navy Electricity and Electronics Training Series (NEETS) . If you are looking for a reviewer in Electronics Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.

### Start Practice Exam Test Questions

Choose the letter of the best answer in each questions.

1. Alternating current can be defined as current that varies in

• A. amplitude and direction
• B. magnitude and phase
• C. amplitude and time
• D. time and phase

2. Before a 120-volt dc source can be used to power a 12-volt load, the voltage must be reduced. Which of the following methods can be used?

• A. A resistor placed in parallel with the load
• B. A resistor placed in series with the load
• C. A step-down transformer placed in series with load
• D. A step-down transformer placed in parallel-with the load

3. Alternating current has replaced direct current in modern transmission systems because it has which of the following advantages?

• A. Ac can be transmitted with no line loss
• B. Ac can be transmitted at higher current levels
• C. Ac can be transmitted at lower voltage levels
• D. Ac can be readily stepped up or down

4. A waveform is a graphic plot of what quantities?

• A. Current versus time
• B. Amplitude versus time
• C. Voltage versus amplitude
• D. Magnitude versus amplitude

5. Which of the following properties surrounds a current-carrying conductor?

• A. A magnetic field
• B. A repulsive force
• C. An attractive force
• D. An electrostatic field

9. Which of the following statements accurately describes the magnetic field surrounding a current-carrying conductor?

• A. It is parallel to and equal along all parts of the conductor
• B. It is parallel to and maximum at the most negative part of the conductor
• C. It is perpendicular to and equal along all parts of the conductor
• D. It is perpendicular to the conductor and maximum at the most negative point of the conductor

10. Which of the following factors determine(s) the intensity of a magnetic field surrounding a coil?

• A. The amount of current flow through the coil
• B. The type of core material
• C. The number of turns in the conductor
• D. All of these

11. When you grasp a coil in your left hand with your thumb pointing in the direction of the north pole, your fingers will be wrapped around the coil in the direction of the

• A. voltage potential
• B. magnetic field
• C. current flow
• D. south pole

12. The power consumed in a conductor in realigning the atoms which set up the magnetic field is known as what type of loss?

• A. Hysteresis loss
• B. Magnetic loss
• C. Field loss
• D. Heat loss

13. The magnetic field surrounding a straight conductor is (a) what shape, and (b) is in what position relative to the conductor?

• A. (a) Linked oblong (b) Parallel
• B. (a) Concentric circles (b) Parallel
• C. (a) Linked oblong (b) Perpendicular
• D. (a) Concentric circles (b) Perpendicular

14. Why is a two-pole magnetic field set up around a coil?

• A. Because separate lines of magnetic force link and combine their effects
• B. Because concentric lines of force cross at right angles and combine.
• C. Because lines of force are separated and bent at the coil ends
• D. Because separate lines of force are attracted to the two poles of the coil

15. When a conductor is moving parallel to magnetic lines of force, (a) what relative number of magnetic lines are cut, and (b) what relative value of emf is induced?

• A. (a) Minimum, (b) maximum
• B. (a) Minimum, (b) minimum
• C. (a) Maximum, (b) maximum
• D. (a) Maximum, (b) minimum

16. When the induced voltage in a conductor rotating in a magnetic field is plotted against the degrees of rotation, the plot will take what shape?

• A. A circle
• B. A sine curve
• C. A square wave
• D. A straight line

17. When a loop of wire is rotated through 360º in a magnetic field, the induced voltage will be zero at which of the following points?

• A. 45º
• B. 90º
• C. 180º
• D. 270º

18. When a loop of wire is rotated 360º in a magnetic field, at what points will the induced voltage reach its maximum (a) positive, and (b) negative values?

• A. (a) 0º , (b) 180º
• B. (a) 0º , (b) 270º
• C. (a) 90º , (b) 180º
• D. (a) 90º , (b) 270º

19. When a coil of wire makes eight complete revolutions through a single magnetic field, (a) what total number of alternations of voltage will be generated

and, (b) what total number of cycles of ac will be generated?

• A. (a) 32, (b) 16
• B. (a) 16, (b) 8
• C. (a) 8, (b) 4
• D. (a) 4, (b) 2

20. According to the left-hand rule for generators, when your thumb points in the direction of rotation, your (a) forefinger and (b) your middle finger will indicate the relative directions of what quantities?

• A. (a) Current, (b) Magnetic flux, south to north
• B. (a) Current, (b) Magnetic flux, north to south
• C. (a) Magnetic flux, south to north, (b) Current
• D. (a) Magnetic flux, north to south, (b) Current

21. Continuous rotation of a conductor through magnetic lines of force will produce what type of (a) voltage and (b) waveform?

• A. (a) Ac, (b) sine wave
• B. (a) Dc, (b) continuous level
• C. (a) Ac, (b) sawtooth
• D. (a) Dc, (b) pulsating wave

22. What is the term for the number of complete cycles of ac produced in one second?

• A. Period
• B. Waveform
• C. Frequency
• D. Wavelength

23. What is the unit of measurement for frequency?

• A. Cycle
• B. Hertz
• C. Period
• D. Maxwell

24. A loop of wire rotating at 60 rpm in a magnetic field will produce an ac voltage of what frequency?

• A. 1 Hz
• B. 60 Hz
• C. 120 Hz
• D. 360 Hz

25. An ac voltage of 250 hertz has a period of

• A. 0.004 second
• B. 0.025 second
• C. 0.4 second
• D. 2.5 seconds

26. What is the approximate frequency of an ac voltage that has a period of .0006 second?

• A. 6 Hz
• B. 16.67 Hz
• C. 600 Hz
• D. 1667 Hz

37. An ac voltage has a frequency of 350 Hz. In two seconds, what total number of times will the peak value of voltage be generated?

• A. 350 times
• B. 700 times
• C. 1400 times
• D. 2800 times

38. The value of current of an ac waveform taken at any particular moment of time is what type of value?

• A. Average value
• B. Effective value
• C. Instantaneous value
• D. Peak-to-peak value

39. While the value of an ac voltage may be expressed as one of several values, the accepted practice is to express it as what type value?

• A. Average value
• B. Instantaneous value
• C. Peak-to-peak value
• D. Effective value

40. The total of ten instantaneous values of an alternation divided by ten is equal to what value?

• A. The peak value
• B. The average value
• C. The instantaneous value
• D. The effective value

41. Which of the following mathematical formulas is used to find the average value of voltage for an ac voltage?

• A. Eavg = 0.707 x Emax
• B. Eavg = 1.414 x Eeff
• C. Eavg = 0.636 x Emax
• D. Eavg = 0.226 x Eeff

42. What is the average value of all of the instantaneous voltages occurring during one cycle of an ac waveform with a peak value of 60 volts?

• A. 0 volts
• B. 38 volts
• C. 76 volts
• D. 128 volts

43. If an ac voltage has an Emax of 220 volts, what is Eavg?

• A. 50 volts
• B. 140 volts
• C. 156 volts
• D. 311 volts

44. If an ac waveform has a peak-to-peak value of 28 volts, what is Eavg?

• A. 40 volts
• B. 20 volts
• C. 18 volts
• D. 9 volts

45. If an ac waveform has a peak value of 4.5 amperes, what is its average value?

• A. 2.9 amperes
• B. 3.2 amperes
• C. 5.7 amperes
• D. 6.4 amperes

46. If the average value of current of an ac waveform is 1.2 amperes, what is its maximum value of current?

• A. 0.8 amperes
• B. 0.9 amperes
• C. 1.7 amperes
• D. 1.9 amperes

47. The value of alternating current that will heat a resistor to the same temperature as an equal value of direct current is known as

• A. Iavg
• B. Ieff
• C. Iin
• D. Imax

48. The rms value for an ac voltage is equal to what other ac value?

• A. Eavg
• B. Emax
• C. Eeff
• D. Ein

49. What value will result by squaring all values for Einst, averaging these values, and then taking the square root of that average?

• A. Eavg
• B. Emax
• C. Eeff
• D. Ein

50. The accepted, nominal value for household power in the United States is 120-volts, 60 Hz. What is the value of maximum voltage?

• A. 170 volts
• B. 120 volts
• C. 85 volts
• D. 76 volts

51. An ac voltmeter is usually calibrated to read which of the following ac values?

• A. Average
• B. Effective
• C. Peak
• D. Peak-to-peak

52. If the maximum value for an ac voltage is known, the Eeff can be found by using which of the following formulas?

• A. Eeff = Emax/0.636
• B. Eeff = Emax/0.707
• C. Eeff = Emax x 0.707
• D. Eeff = Emax x 1.414

53. If the Ieff of an ac waveform is 3.25 amperes, what is Imax?

• A. 4.6 amperes
• B. 2.3 amperes
• C. 2.1 amperes
• D. 1.6 amperes

54. If the rms value of the voltage of an ac waveform is 12.4 volt what is its average value? (Hint: compute Emaxfirst.)

• A. 8 volts
• B. 11 volts
• C. 15 volts
• D. 18 volts

61. Which of the following is an important rule to remember when using Ohm’s Law to solve ac circuit problems?

• A. Always solve for resistance first
• B. Give the answer as effective value
• C. Never mix values
• D. Convert all given values to effective before attempting to solve

62. An ac circuit is composed of three 20 – ohm resistors connected in parallel. The average voltage supplied to this circuit is 62-volts ac. What is the maximum current?

• A. 9.3 amperes
• B. 14.6 amperes
• C. 17.5 amperes
• D. 22.5 amperes

63. If the ac source in question 1-62 is raised to an average value of 120 volts, what is the Ieff?

• A. 11.48 amperes
• B. 12.70 amperes
• C. 20.01 amperes
• D. 25.52 amperes

64. If Eeff is 150 volts and Imax is 4.5 amperes, what is the total resistance (RT) of a circuit?

• A. 21.2
• B. 23.6
• C. 33.3
• D. 47.1

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