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CHAPTER 4 – CIRCUIT COMPONENTS NAME: DATE: Define each of the following terms from Chapter Four of the text book. Read the passages and include any additional information that may assist you on an exam such as symbols or base units. Some of the terms may need to be defined by reading the surrounding text. Battery Cell Electrodes Electrolytes Ampere-Hours Secondary Cells Dry Cell Wet Cell Internal Resistance Cell (or battery) capacity Depolarizing agent Group of plates Rate of charge Specific Gravity Chapter 4 – Circuit Components Page 1 Hydrometer Charge/discharge cycles Shelf life Voltage standard Light loads Light-emitting diodes Neon glow lamps Incandescent lamps Tungsten filament Life Rated voltage Lumens Current ratings Ionization External Resistor Current-limiting resistors Chapter 4 – Circuit Components Page 2 Polarized device Potentiometer Nonlinear tapers Rheostats Adjustable resistors Tapped resistors Power rating Safety factor Tolerances Color codes Surface-mount devices Reliability Normally open Normally Closed SPDT Rotary switches Chapter 4 – Circuit Components Page 3 Shorting Cable Wire Solid Conductor Stranded Conductor Shielding Coaxial cable Flat ribbon Gage number Maximum temperature rating Short circuit Dead short Grounded Current rating Fuse Blowing characteristic Chapter 4 – Circuit Components Page 4 Fast-blow fuses Medium-blow fuses Slow-blow fuses Instrument fuses Resettable fuses Thermal circuit breakers Magnetic circuit breakers SUMMARY 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. Cells are energy or power sources. Cells provide dc voltage. A cell contains an electrolyte and two electrodes. A battery is made from two or more cells. Primary cells are not rechargeable. Secondary cells are rechargeable. Dry cells may use either a paste or a liquid electrolyte. Gases are produced when cells are charged or discharged. The energy storage capacity of a cell or battery is expressed in ampere-hours. The energy available from a battery is dependent on temperature, rate of discharge, and final voltage. Internal resistance causes a cell's voltage to decrease as the current increases. Polarization refers to the buildup of gas ions around an electrode. Common secondary cells are lead-acid, nickel-cadmium, and rechargeable alkaline. Common primary cells are carbon-zinc, alkaline, mercury, and silver oxide. When a lead-acid cell is discharging, sulfuric acid is being converted to water. Specific gravity is measured by a hydrometer. Safety glasses should be work when working with lead-acid cells and batteries. Electrolyte on the skin or clothing should be immediately removed by flushing with lots of water. Carbon-zinc cells are relatively inexpensive. Alkaline cells store more energy than carbon-zinc cells. The former are more efficient at high current drains. Both mercury and silver oxide cells have nearly constant output voltage. Incandescent miniature lamps have tungsten filaments. Miniature lamps have both a current and a voltage rating. Bimetallic strips bend because the two metals have different coefficients of expansion. The resistance of a lamp when hot is greater than its resistance when cold. Only one electrode glows when a neon lamp is operated on direct current. Both a neon lamp and a light-emitting diode (LED) circuit must have a resistor to limit the current through the device. A potentiometer is a variable resistor. A potentiometer can also be used as a rheostat. The power rating of a resistor is independent of its resistance. Common types of resistors are carbon-composition, cermet, wire-wound, deposited-film, and conductive-plastic. Chapter 4 – Circuit Components Page 5 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. Resistance values and tolerances are indicated with a color code on the body of a resistor. Thermistors have high temperature coefficients. Common types of small switches are rotary, toggle, slide, rocker, and push-button. Spring-loaded, momentary-contact switches can be either normally open or normally closed. Rotary switches can handle complex switching involving many circuits. Switches have both a current and a voltage rating. Cables are multiple conductors. Wires are single conductors. Conductors may be stranded or solid. Shielded wires and cables are used to help isolate a conductor's electromagnetic fields. Coaxial cables are used to connect antennas to receivers or transmitters. The American wire gage is the standard used to specify the size of a conductor. The cross-sectional area of a conductor is specified in circular mils. When the gage of a conductor is decreased by three gage numbers, its cross-sectional area doubles. Its resistance is half as much. Insulation used on conductors has both a temperature and a voltage rating. Circuit-breaker mechanisms work on either a magnetic or a thermal principle. Fuses are thermally operated devices. A blown fuse results in an open circuit. Instrument (fast-blow) fuses are used to protect electric meters. Resettable fuses do not produce an open circuit when tripped. SMDs are smaller than traditional components. Fuses and breakers have both current and voltage ratings. The characteristics of various dry cells are given in Table 4-2. Table 4-2 Cell Type Carbon-zinc Alkaline Mercury Silver oxide Lithium Rechargeable alkaline Nickel-cadmium Dry Cell Characteristics Rated Voltage during Voltage Discharge 1.5 1.5 1.35 1.5 2.5 - 3.6 1.5 Decreases Decreases Almost constant Almost constant Almost constant Decreases 1.25 Decreases slightly Chapter 4 – Circuit Components Cycle Life Initial Cost Energy-toWeight Ratio Low Low Med High High High Med Internal Resistanc e Med Low Low Low Med high Very low High High Very low Low Med Med High High Very high Low Page 6