FCC Study

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FCC Study
2012-05-21 23:38:28
Element part

Questions to 1st chapter homework for Element 3
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  1. The product of the readings of an AC voltmeter and AC ammeter is called?
    Apparent power
  2. What is the basic unit of electrical power?
  3. What is the term used to express the amount of electrical energy stored in an electrostatic field?
  4. What determines the strength of the magnetic field around a conductor?
    The amount of current.
  5. What will produce a magnetic field?
    A current flowing through a conductor.
  6. When induced currents produce expanding magnetic fields around conductors in a direction that opposes the original magnetic filed, this is known as?
    Lenz's law
  7. Skin effect is the phenomenon where?
    RF current flows in a thin layer of the conductor, closer to the surface, as frequency increases.
  8. Which of these will be most useful for insulation at UHF frequencies?
  9. Which of the 4 groups of metals listed below are the best low- resistance conductors?
    Gold, silver, and copper
  10. What is the purpose of a bypass capacitor?
    It removes alternating current by providing a low impedance path to ground.
  11. How would you calculate the total capacitanc of three capacitors in parallel?
    Ct = C1+ C2+ C3
  12. What are the two most commonly- used specifications for a junction diode?
    Maximum forward current and PIV (peak inverse voltage.)
  13. What are the two basic types of junction field- effect transistors?
    N- channel and P- channel
  14. How does the input impedance of a field- effect transistor compare with that of a bipolar transistor?
    An FET has high input impedance; a bipolar transistor has low input impedance.
  15. An AC ammeter indicates:
    Effective (RMS) values of current
  16. *By what factor must the voltage of an AC circuit, as indicated on the scale of an AC voltmeter, be multiplied to obtain the peak voltage value?
  17. *What is the easiest voltage amplitude to measure by viewing a pure sine wave signal on an oscilloscope?
    Peak- to- peak
  18. What is a sine wave?
    A wave following the laws of the trigonometric tangent function.
  19. How many degrees are there in one complete sine wave cycle?
    360 degrees.
  20. What type of wave is characterized by a rise time significantly faster than the fall time (or vise versa?)
    Sawtooth wave
  21. What is the term used to identify an AC voltage that would cause the same heating in a resistor as a corresponding value of DC voltage?
    Root mean square (RMS)
  22. Halving the cross- sectional area of a conductor will?
    Double the resistance.
  23. How do you compute true power (power dissipated in the circuit) in a circuit where AC voltage and current are out of phase?
    Multiply apparent power times the power factor.
  24. What value of series resistor would be needed to obtain a full scale deflection on a 50 microamp DC meter with an applied voltage of 200 volts DC?
    4 megohms
  25. Which of the following Ohms Law formulas is incorrect?
    I = R / E

    • Correct formulas:
    • R = E / I
    • E = I * R
    • I = E / R
  26. If a current of 2 amperes flows through a 50- ohm resistor, what is the voltage across the resistor?
    100 volts
  27. What is the peak- to- peak RF voltage on the 50 ohm output of a 100 watt transmitter?
    200 volts
  28. What is the maximum DC or RMS voltage that may be connected across a 20 watt, 2000 ohm resistor?
    200 volts
  29. What is the maximun rated current- carrying capacity of a resistor marked "2000 ohms, 200 watts?"
    0.316 amps
  30. What is the most the actual transmit frequency could differ from a reading of 462,100,000 hertz on a frequency counter with a time base accuracy of plus or minus 0.1 ppm?
    46.21 Hz
  31. The second harmonic of a 380 kHz frequency is:
    760 kHz
  32. What is the most the actual transmitter frequency could differ from a reading of 156,520,000 hertz on a frequency counter with a time base accuracy of +/ - 10 ppm?
    1565.20 Hz
  33. At 150 degrees, what is the amplitude of a sine- wave having a peak value of 5 volts?
    + 2.5 volts
  34. What is the equivalent to the root- mean- square value of an AC voltage?
    The DC voltage causing the same heating in a given resistor as the RMS AC voltage of the same value.
  35. Determine the phase relationship between the two signals shown in Figure.
    B is lagging A by 90 degrees.
  36. If a resistance to which a constant voltage is applied is halved, what power dissipation will result?
  37. In a circuit where the AC voltage and current are out of phase, how can the true power be determined.
    By multiplying the apparent power times the power factor.
  38. What does the power factor equal in an R- L circuit having a 30 degree phase angle between the voltage and the current?
  39. What is the term for the time required for the current in an RL circuit to build up to 63.2% of the maximum value?
    One time constant.
  40. After two time constants, the capacitor in an RC circuit is discharged to what percentage of the starting voltage?
  41. What is the time constant of a circuit having two 220- microfarad capacitors and two 1- megohm resistors all in parallel?
    220 seconds
  42. What is the time constant of a circuit having a 220- microfarad capacitor and a 1- megohm resistor in parallel?
    220 seconds
  43. What is the time constant of a circuit having two 220- microfarad capacitors and two 1- megohm resistors in series?
    220 seconds
  44. What is the impedance of a network composed of a 0.1- microhenry inductor in series with a 20- ohm resistor, at 30 MHz? Specify your answer in rectangular coordinates.
    20 +j19
  45. In rectangular coordinates, what is the impedance of a network composed of a 10- microhenry inductor in series with a 40- ohm resistor, at 500 MHz?
    40 +j31400
  46. In polar coordinates, what is the impedance of a network composed of a 400- ohm- reactance capacitor in series with a 300- ohm resistor?
    500- ohm, / -53.1 degrees
  47. In polar coordinates, what is the impedance of a network composed of a 300- ohm- reactance capacitor, a 600- ohm- reactance inductor, and a 400- ohm resistor, all connected in series.
    500 ohms, /37 degrees
  48. Using the polar coordinate system, what visual representation would you get of a voltage in a sinewave circuit?
    The plot shows the magnitude and phase angle.
  49. A 1- watt, 10 volt Zener diode with the following characteristics: Imin = 5mA; Imax = 95 mA; and Z = 8 ohms, is uesed as part of a voltage regulator in a 20- V power supply. Approximately what size current- limiting resistor would be used to set its bias to the midpoint of its operation range?
    200 ohms
  50. Given a power supply with a no load voltage of 12 volts and a full load voltage of 10 volts, what is the percentage of voltage regulation?
  51. What is the conductance (G) of a circuit if 6 amperes of current flows when 12 volts DC is applied?
    .50 Siemens (mhos) (6 is .50 of 12)
  52. What is the photoconductive effect?
    The increased conductivity of an illuminated semiconductor junction.
  53. What is the description of an optoisolator?
    An LED and a photosensitive device.
  54. What happens to the conducitivity of a photosensitive semiconductor junction when it is illuminated?
    The junction resistance decreases.
  55. What factors determine the capacitance of a capacitor?
    Distance between the plates and the dielectric constant of the material between the plates.
  56. In figure shown, which component (labeled 1 through 4) is used to provide a signal ground?
  57. What is the purpose of a coupling capacitor?
    It blocks direct current and passes alternating current.
  58. A tranformer primary of 2250 turns connected to 120 VAC will develop what voltage across a 500- turn secondary?
    26.7 volts
  59. A power transformer has a primary winding of 200 turns of 24# wire and a secondary winding consisting of 500 turns of the same size wire. When 20 volts are applied to the primary winding, the expected secondary voltage will be:
    50 voltage
  60. What are the three terminals of an SCR?
    Anode, cathode, and gate
  61. What circuit might contain a SCR?
    A light- dimming circuit.
  62. What type of semiconductor diode varies its internal capacitance as the voltage applied to its terminals varies?
    Varactor diode
  63. What is the approximate magnitude of the impedance of a parallel R- L- C circuit at resonance?
    Approximately equal to the circuit resistance.
  64. How could voltage be greater across reactance's in series than the applied voltage?
  65. What is the characteristic of the current flow within the parallel elements in a parallel R- L- C circuit at resonance?
  66. What is the main advantage of using an op- amp audio filter over a passive LC audio filter?
    Op- amps exhibit gain rather than insertion loss.
  67. Which of the following op- amp circuits is operated open- loop?
  68. In the op- amp oscillator circuit shown in Figure, what would be the most noticeable effect if the capacitance of C were suddenly doubled?
    Frequency would be lower
  69. What frequency synthesizer circuit uses a phase comparator, look- up table, digital- to- analog converter, and a low- pass antialias filter?
    A direct digital synthesizer.
  70. What spectral impurity components might be generated by a phase- locked- loop synthesizer?
    Broadband nosie
  71. What is the definition of a phase- locked loop (PLL) circuit?
    A servo loop consisting of a phase detector, a low- pass filter and voltage- controlled oscillater.
  72. Which lamps would be lit in the circuit shown in Figure?
    2, 3, 4, 7, and 8
  73. In Figure with a square wave input what would be the output?
  74. With a pure AC signal input to the circuit shown in Figure, what output wave form would you expect to see on an oscilloscope display?
  75. What is the voltage range considered to be valid logic low input in a TTL device operation at 5 volts?
    Zero to 0.8 volts
  76. TTL inputs left open develop what logic state?
    A high- logic state.
  77. What is a characteristic of an AND gate?
    Produces a logic "1" as its output only if all inputs are logic "1"
  78. What is a characteristic of an NOR gate?
    Produces a logic "0" at its output when the input is logic "1" and vice versa.
  79. What is a characteristic of an NOT gate?
    Produces a logic "0" at its output when the input is logic "1" and vice versa.
  80. For the logic input levels shown in Figure, what are the logic levels of test A, B and C in this circuit?
    A is low, B is high and C is high.
  81. In a positive- logic circuit, what level is used to represent a logic 1?
    High level
  82. Given the input levels shown in Figure and assuming positive logic devices, what would the output be?
    A is low, B is high and C is high.
  83. A flip- flop circuit is a binary logic element with how many stable states?
  84. How many bits of information can be stored in a single flip- flop circuit?
  85. An R- S flip- flop is capable of doing all of the following except:
    Operate in toggle mode with R- S inputs with CLK initiated.
  86. What is an astable multivibrator?
    A circuit that alternates between two unstable states.
  87. What is a monostable vibrator?
    A circuit that can be switched momentarily to the opposite binary state and then returns after a set time to its original state.
  88. What is a bistable multivibrator circuit commonly named?
    Flip- flop
  89. What is the name of the semiconductor memory IC whose digital data can be written or read and whose memory word address can be accessed randomly?
    RAM- Random Access Memory
  90. What is the name of the semiconductor IC that has a fixed pattern of digital data stored in its memory matrix?
    ROM- Read - Only Memory
  91. What does the term "IO" mean within a microprocessor system?
    Input- output
  92. In a microprocessor- controlled two- way radio, a "watchdog" timer
    Verifies that the microprocessor is executing the program
  93. What portion of a microprocessor circuit is the pulse generator?
  94. What circuit interconnects the microprocessor with the memory and input/output system?
    Data bus line
  95. What is the function of a decade counter digital IC?
    Produce one output pulse for every ten input pulses.
  96. What integrated circuit device converts an analog signal to digital signal?
    A D C (analog to digital converter)
  97. In binary numbers, how would you note the quantity TWO?