Module 1

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bugsbunny2255
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121051
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Module 1
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2011-12-05 22:18:56
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  1. What is matter, and in what three states is it found?
    Anything that occupies space and has weight. Solids, liquids, gases.
  2. What is an element?
    A substance which cannot be reduced to a simpler substance by chemical means.
  3. What is a compound?
    A substance consisting of two or more elements.
  4. What is the difference between a compound and a mixture?
    A compound is a chemical combination of elements that cannot be separated by physical means. A mixture is a physical combination of elements and compounds that are not chemically combined.
  5. What is a molecule?
    A chemical combination of two or more atoms.
  6. What are the three types of subatomic particles, and what are their charges?
    Electrons-negative, protons-positive, and neutrons-neutral.
  7. What is energy of motion called?
    Kinetic energy
  8. How is invisible light changed to visible light in a fluorescent light?
    Invisible light photons (ultraviolet) bombard the phosphor atom in the light tube. The phosphor atoms emit visible light photons.
  9. What determines the valence of an atom?
    The number of electrons in the outer shell.
  10. What is an ion?
    An atom with more or less than its normal number of electrons.
  11. What determines whether a substance is a conductor or an insulator?
    The number of valence electrons.
  12. How is a negative charge created in a neutral body?
    Through the accumulation of excess electrons.
  13. How are static charges created?
    By friction.
  14. What is the electrical charge of an atom which contains 8 protons and 11 electrons
    Negative.
  15. What is the relationship between charged bodies?
    Like charges repel, and unlike charges attract with a force directly proportional to the product of their charges and inversely proportional to the square of the distance between them.
  16. What is an electrostatic field?
    The space between and around charged bodies.
  17. In what direction are electrostatic lines of force drawn?
    Leaving positive, entering negative.
  18. What are some examples of electrical equipment which use magnetism?
    Motors, generators, speakers, computers, televisions, tape recorders, and many others.
  19. What are magnetic materials?
    Those materials that are attracted by magnets and have the ability to become magnetized.
  20. What characteristics do all ferromagnetic materials have in common?
    The relative ease with which they are magnetized.
  21. What type of magnetic material should be used to make a temporary magnet?
    A material that exhibits low reluctance and high permeability, such as iron or soft steel.
  22. What is retentivity?
    The ability of a material to retain magnetism.
  23. How does the law of magnetic poles relate to the law of electric charges?
    They are very similar; like charges repel, unlike charges attract, like poles repel —unlike poles attract.
  24. A compass is located at the geographical North Pole. In which direction would its needle point?
    To the magnetic north pole
  25. Using Weber’s molecular theory of magnetism, describe the polarity of the magnetic poles produced by stroking a magnetic material from right to left with the south pole of a magnet
    South pole at the right, north pole at the left
  26. What is the difference between the domain theory and Weber’s theory of magnetism?
    The domain theory is based upon the electron spin principle; Weber’s theory uses the concept of tiny molecular magnets.
  27. What is a magnetic line of force?
    To enable you to "see" the magnetic field.
  28. In what way do magnetic lines of force differ from electrostatic lines of force?
    Electrostatic lines of force do not form closed loops.
  29. How should a delicate instrument be protected from a magnetic field?
    By shielding or surrounding the instrument with a soft iron case, called a magnetic shield or screen.
  30. How should bar magnets be stored?
    In pairs, with opposite poles together to provide a complete path for magnetic flux.
  31. What is the definition of energy?
    The ability to do work.
  32. What type of energy does a rolling stone have?
    Kinetic energy.
  33. What kind of energy does the stone have if it is at rest at the top of a hill?
    Potential energy.
  34. What term describes voltage or emf?
    Difference of potential.
  35. Convert 2.1 kV to volts.
    2100 volts.
  36. Express the following in more simple terms. (a) 250,000 volts, (b) 25,000,000 microvolts, (c) Millivolt.
    (a) 250 kV, (b) 25 V, (c) 1 9_
  37. A device which supplies a voltage is commonly referred to by what name?
    A voltage source.
  38. Name the six methods of producing a voltage.
    Friction, pressure, heat, light, chemical action, and magnetism.
  39. The piezoelectric effect is an example of a voltage being produced by what method?
    Pressure.
  40. A thermocouple is a device that produces voltage by what method?
    Heat.
  41. A battery uses what method to produce a voltage?
    Chemical
  42. A generator uses what method to produce a voltage?
    Magnetic
  43. According to electron theory, an electric current flows from what potential to what
    potential?
    Electron theory assumes that electron flow is from negative to positive.
  44. The effects of directed drift take place at what rate of speed?
    The speed of light (186,000 miles per second, 300,000,000 meters per second).
  45. What is the relationship of current to voltage in a circuit?
    Current increases as voltage increases.
  46. Convert 350 mA to amperes.
    0.35 amperes.
  47. What is the symbol for ohm?
  48. When would silver be used as a conductor in preference to copper?
    When the need for conductivity is great enough to justify the additional expense.
  49. Which wire has the least resistance? Wire A-copper, 1000 circular mils, 6 inches long. Wire B-copper, 2000 circular mils, 11 inches long.
    Wire B.
  50. Which temperature coefficient indicates a material whose resistance increases as temperature increases?
    Positive.
  51. What term describes a material whose resistance remains relatively constant with changes in temperature?
    Zero temperature coefficient.
  52. What is the unit of conductance and what other term is sometimes used?
    The mho (v), siemens.
  53. What is the relationship between conductance and resistance?
    They are reciprocals of each other.
  54. What does the wattage rating of a resistor indicate?
    Its ability to dissipate heat.
  55. What are the two disadvantages of carbon-type resistors?
    1. Change value with age. 2. Limited power capacity.
  56. What type resistor should be used to overcome the disadvantages of the carbon resistor?
    The wire wound resistor.
  57. Describe the differences between the rheostat connections and those of the potentiometer.
    The rheostat may have two connections, one fixed and one moveable; the potentiometer always has three connections, one moveable and two fixed.
  58. Which type of variable resistor should you select for controlling a large amount of current?
    The rheostat.
  59. A carbon resistor has a resistance of 50 ohms, and a tolerance of 5 percent. What are the colors of bands one, two, three, and four, respectively?
    The bands are green, black, black, and gold.
  60. A carbon resistor has the following color bands: The first band is yellow, followed by violet,yellow, and silver. What is the ohmic value of the resistor?
    470,000 ohms (470 kilohms).
  61. The same resistor mentioned in question 63 has a yellow fifth band. What does this signify?
    The resistor’s chance of failure is 0.001 percent for 1000 hours of operation.
  62. A resistor is handed to you for identification with the following color code: the first band is blue, followed by gray, green, gold, and brown. What is the resistor’s value?
    6,800,000 ohms (6.8 megohms), with 5% tolerance, and a 1% reliability level.

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