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Chapter 3

Chapter 3. Introduction to Basic Electrical Circuit Materials. Objectives. Identify different conductor types. Determine the cross-sectional area of a conductor. List the factors affecting resistance. Identify various insulation materials. Objectives. List three special conductor pathways.

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Chapter 3

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  1. Chapter 3 Introduction to Basic Electrical Circuit Materials

  2. Objectives • Identify different conductor types. • Determine the cross-sectional area of a conductor. • List the factors affecting resistance. • Identify various insulation materials. Permission granted to reproduce for educational use only.

  3. Objectives • List three special conductor pathways. • Explain the manufacture of printed circuit boards. • Identify various switching devices. Permission granted to reproduce for educational use only.

  4. Objectives • Identify various lighting devices. • Identify different types of resistors. • Determine the value of color-coded resistors. Permission granted to reproduce for educational use only.

  5. Conductors • Copper • Silver • Aluminum (high-voltage lines) • Brass (electrical-mechanical equipment) Permission granted to reproduce for educational use only.

  6. Conductors (Cont.) • Transfer electrons from one atom to another within the conductor Permission granted to reproduce for educational use only.

  7. G = 1/R G: conductance in siemens R: resistance in ohms Computing Electrical Conductance Permission granted to reproduce for educational use only.

  8. Lesson in Safety • Your body can conduct electricity • Electric current can flow into one hand, through your body, and out your other hand • Can be fatal • Keep one hand in a pocket to avoid shock • Stand on insulated materials when working with high voltage Permission granted to reproduce for educational use only.

  9. Conductor Sizes • Gauged by cross-sectional area • Determine amount of current the conductor can handle before overheating • Circular mil system Permission granted to reproduce for educational use only.

  10. Circular Mils (cmils) • 1 mil= 0.001 inches Permission granted to reproduce for educational use only.

  11. Conductor Insulation • Insulators • Insulation on conductors as protective coating • Codings Permission granted to reproduce for educational use only.

  12. Code letters R rubber H heat HH high heat A asbestos T thermoplastic M oil resistant UF underground feeder C corrosion resistant Color coding Used to trace the insulation through a building Can represent certain voltages, polarities, or grounding conductors Governed by building codes or manufacturing associations Insulation Codings Permission granted to reproduce for educational use only.

  13. Types of Conductors Permission granted to reproduce for educational use only.

  14. Conductor Resistance • Cross-sectional area of a conductor • Type of material • Length of conductor • Temperature of material Permission granted to reproduce for educational use only.

  15. Cross-Sectional Area of a Conductor • Larger diameter has a greater current and lower resistance Permission granted to reproduce for educational use only.

  16. Type of Material • Affects conductance and resistance Permission granted to reproduce for educational use only.

  17. Length of Conductor • The longer the conductor is, the more resistance it has Permission granted to reproduce for educational use only.

  18. Temperature of Material • Metals increase in resistance as ambient temperature rises • Metals exposed to low temperatures become superconductors Permission granted to reproduce for educational use only.

  19. Safety Organizations and Standards • National Fire Protection Agency (NFPA) • National Electrical Code • Underwriters Laboratories Inc. • Occupational Safety and Health Administration • Conductor voltage drop standard Permission granted to reproduce for educational use only.

  20. National Fire Protection Agency • NFPA dedicated to fire protection • Provides information on how fires are started • Provides specific prevention methods • Produces National Electrical Code Permission granted to reproduce for educational use only.

  21. National Electrical Code • Regulations to ensure safety • Standards apply to design of electrical systems • Adopted by government agencies at city, county, state, and federal levels Permission granted to reproduce for educational use only.

  22. Underwriters Laboratories Inc. • Independent organization that conducts tests for public safety • Tests equipment for minimal safety design standards Permission granted to reproduce for educational use only.

  23. Occupational Safety and Health Administration • Part of U.S. Department of Labor • Responsible for worker safety • Conducts on-site inspections • Authority to inspect and fine industries that do not meet safety standards Permission granted to reproduce for educational use only.

  24. Conductor Voltage Drop • NEC’s maximum voltage drop standard for branch circuits • A 3% voltage drop is the maximum permissible • CMA: area in cmils • K: material constant • I: amperage • L: length of wire • VD: voltage drop Permission granted to reproduce for educational use only.

  25. Review What are conductors? Pathways that allow current to flow through an electrical circuit Permission granted to reproduce for educational use only.

  26. Review What are four materials of which conductors are typically made? Copper, silver, aluminum, and brass Permission granted to reproduce for educational use only.

  27. Review What is the unit used to measure conductance? The siemens Permission granted to reproduce for educational use only.

  28. Review What unit is used to measure conductor sizes? Circular mils (cmils) Permission granted to reproduce for educational use only.

  29. Review What materials do not conduct electrons well? Insulators Permission granted to reproduce for educational use only.

  30. Review What is ambient temperature? Temperature of material surrounding the conductor, such as air, water, or soil Permission granted to reproduce for educational use only.

  31. Review What organization produces the National Electrical Code? National Fire Protection Agency (NFPA) Permission granted to reproduce for educational use only.

  32. Review What organization inspects equipment to award its seal of approval? Underwriters Laboratories Inc. Permission granted to reproduce for educational use only.

  33. Special Conductor Pathways • Breadboards • Printed circuit boards (PCBs) • Chassis Permission granted to reproduce for educational use only.

  34. Breadboards • Provide an easy system for constructing circuits quickly • Copper strips beneath the holes are conductor pathways • Proto boards Permission granted to reproduce for educational use only.

  35. Printed Circuit Boards (PCBs) • Strips of conductor material attached to an insulated board • Components are soldered to conductive strips Permission granted to reproduce for educational use only.

  36. Construction of PCBs • Copper foil used as conductor material • Resist material put on copper foil for circuit design • Etchant removes all of copper but circuit design • Photographic process uses light exposure and solvent to make circuit design Permission granted to reproduce for educational use only.

  37. Chassis • Older way of mounting components • Part of the circuitry • Not commonly used as a conductor, but still used in cars Permission granted to reproduce for educational use only.

  38. Review What is a breadboard? A pathway that consists of a series of holes aligned in rows across the entire surface of an insulation material Permission granted to reproduce for educational use only.

  39. Review What is made from a thin layer of conductor material, cut into strips, and attached to an insulated board? Printed circuit board (PCB) Permission granted to reproduce for educational use only.

  40. Common Circuit Devices • Switches • Connectors • Circuit protection devices Permission granted to reproduce for educational use only.

  41. Switches • Controlled by actuators • Single-polesingle-throw (SPST) • Single-pole double-throw (SPDT) • Double-pole double-throw (DPDT) Permission granted to reproduce for educational use only.

  42. Switch Ratings • Ampacity rating • Voltage rating • Exceeding ratings causes switch to fail Permission granted to reproduce for educational use only.

  43. Connectors • Vary by type or size of conductors • Solderless connectors are common Permission granted to reproduce for educational use only.

  44. Connectors (Cont.) • Mechanical connection to larger conductors Permission granted to reproduce for educational use only.

  45. Circuit Protection Devices • Fuses • Circuit breakers Permission granted to reproduce for educational use only.

  46. Fuses • Time required to melt fuse link is inversely proportional to amount of overload Permission granted to reproduce for educational use only.

  47. Circuit Breakers • Resets • Tripping methods • Bimetallic strips • Magnetism Permission granted to reproduce for educational use only.

  48. Review How are switches controlled? By actuators Permission granted to reproduce for educational use only.

  49. Review What is the simplest type of switch? Single-pole single-throw (SPST) Permission granted to reproduce for educational use only.

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