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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. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Objectives • List three special conductor pathways. • Explain the manufacture of printed circuit boards. • Identify various switching devices. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Objectives • Identify various lighting devices. • Identify different types of resistors. • Determine the value of color-coded resistors. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Conductors • • • • Copper Silver Aluminum (high-voltage lines) Brass (electrical-mechanical equipment) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Conductors (Cont.) • Transfer electrons from one atom to another within the conductor © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Computing Electrical Conductance • G = 1/R © Goodheart-Willcox Co., Inc. • G: conductance in siemens • R: resistance in ohms Permission granted to reproduce for educational use only. 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 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Conductor Sizes • Gauged by cross-sectional area • Determine amount of current the conductor can handle before overheating • Circular mil system © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Circular Mils (cmils) • 1 mil = 0.001 inches © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Conductor Insulation • Insulators • Insulation on conductors as protective coating • Codings © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Insulation Codings • Code letters – – – – – – – R H HH A T M UF –C © Goodheart-Willcox Co., Inc. rubber heat high heat asbestos thermoplastic oil resistant underground feeder 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 Permission granted to reproduce for educational use only. Types of Conductors © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Conductor Resistance • • • • Cross-sectional area of a conductor Type of material Length of conductor Temperature of material © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Cross-Sectional Area of a Conductor • Larger diameter has a greater current and lower resistance © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Type of Material • Affects conductance and resistance © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Length of Conductor • The longer the conductor is, the more resistance it has © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Temperature of Material • Metals increase in resistance as ambient temperature rises • Metals exposed to low temperatures become superconductors © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Safety Organizations and Standards • • • • National Fire Protection Agency (NFPA) National Electrical Code Underwriters Laboratories Inc. Occupational Safety and Health Administration • Conductor voltage drop standard © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. National Fire Protection Agency • NFPA dedicated to fire protection • Provides information on how fires are started • Provides specific prevention methods • Produces National Electrical Code © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. 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 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Underwriters Laboratories Inc. • Independent organization that conducts tests for public safety • Tests equipment for minimal safety design standards © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. 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 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Conductor Voltage Drop • NEC’s maximum voltage drop standard for branch circuits • A 3% voltage drop is the maximum permissible KIL CMA VD • • • • • CMA: area in cmils K: material constant I: amperage L: length of wire VD: voltage drop © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What are conductors? Pathways that allow current to flow through an electrical circuit © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What are four materials of which conductors are typically made? Copper, silver, aluminum, and brass © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is the unit used to measure conductance? The siemens © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What unit is used to measure conductor sizes? Circular mils (cmils) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What materials do not conduct electrons well? Insulators © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is ambient temperature? Temperature of material surrounding the conductor, such as air, water, or soil © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What organization produces the National Electrical Code? National Fire Protection Agency (NFPA) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What organization inspects equipment to award its seal of approval? Underwriters Laboratories Inc. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Special Conductor Pathways • Breadboards • Printed circuit boards (PCBs) • Chassis © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Breadboards • Provide an easy system for constructing circuits quickly • Copper strips beneath the holes are conductor pathways • Proto boards © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Printed Circuit Boards (PCBs) • Strips of conductor material attached to an insulated board • Components are soldered to conductive strips © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. 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 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Chassis • Older way of mounting components • Part of the circuitry • Not commonly used as a conductor, but still used in cars © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. 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 © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is made from a thin layer of conductor material, cut into strips, and attached to an insulated board? Printed circuit board (PCB) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Common Circuit Devices • Switches • Connectors • Circuit protection devices © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Switches • Controlled by actuators • Single-pole singlethrow (SPST) • Single-pole doublethrow (SPDT) • Double-pole doublethrow (DPDT) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Switch Ratings • Ampacity rating • Voltage rating • Exceeding ratings causes switch to fail © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Connectors • Vary by type or size of conductors • Solderless connectors are common © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Connectors (Cont.) • Mechanical connection to larger conductors © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Circuit Protection Devices • Fuses • Circuit breakers © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Fuses • Time required to melt fuse link is inversely proportional to amount of overload © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Circuit Breakers • Resets • Tripping methods – Bimetallic strips – Magnetism © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review How are switches controlled? By actuators © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is the simplest type of switch? Single-pole single-throw (SPST) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What are some common actuators? Slide, toggle, rotary, and push button © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What kind of switch has two common connection points and can provide two circuit paths simultaneously? Double-pole double-throw (DPDT) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What are two types of switch ratings? Ampacity and voltage © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What are two common circuit protection devices? Fuses and circuit breakers © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is another name for a circuit breaker? A reset © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Lighting • Types of lighting systems – Incandescent lamps – Discharge lamps • Measured in lumens © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Incandescent Lamps • Developed by Thomas Edison • Tungsten filament produces light • Halogen lamps © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Halogen Lamps • Tungsten filaments produce light • Halogen gas makes filament last longer © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Discharge Lamps • Light produced by energizing gases • Types: – Fluorescent lamps – Compact fluorescent lamps – Mercury vapor lamps – Neon lamps – Glow lamps – Strobe lamps © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Fluorescent Lamps • Filament or electrode • Air removed from tube • Tube filled with inert gas and mercury • Mercury vaporized by heat • Ballast in tube limits current © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Compact Fluorescent Lamps (CFLs) • Special fluorescent lamps that can replace incandescent lamps • Lower wattage than incandescent lamps • Less heat given off than incandescent lamps © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Mercury Vapor Lamps • Two electrodes in an arc tube • Mercury and argon gas • Heat from electrodes vaporizes mercury © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Neon Lamps • Two electrodes in a long glass tube • Shaped for various applications • Tube filled with neon gas • High voltage to create current • Other gases can be used for different colors © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Glow Lamps • • • • Similar to neon lamps Two electrodes in a short tube Tube filled with neon or argon Lower voltages than neon lamps © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Strobe Lamps • Various sizes of glass tubes • Discharge of high dc voltage through tube • Exciters help produce electrical arc • Can generate 50,000 watts © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Lumens • Lumens per watt (lpw) • Light ratings – Candelas – Lumens © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What type of lamp is a halogen lamp? Incandescent lamp © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What category of lamps are fluorescent, neon, and mercury? Discharge lamps © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What component in a fluorescent lamp limits current through the tube? A ballast © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What kind of lamp has two electrodes in an arc tube that help vaporize the gas? Mercury lamp © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review How are different colors achieved in a neon lamp? Different gases are used © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review How are electrical arcs produced in a strobe lamp? Exciters © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Resistors • Many shapes and sizes • Various values of material’s wattage rating © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Types of Resistors • • • • Molded composition resistors Film resistors, or surface-mounted resistors (SMRs) Wire wound resistors Adjustable resistors – A sliding tap allows the resistance to be varied © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Potentiometers • Rotary knob varies resistance • Found in electronic projects • Similar to wire wound resistors © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Thermistors • Change resistance with temperature • Prevent high current values • Example: blow dryer © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Resistor Color Code • Three to five color bands • Bands represent different values • Fourth band represents tolerance © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is the resistor’s ability to safely dissipate heat? Wattage rating © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What are film resistors also called? Surface-mounted resistors (SMRs) © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What kind of resistors have a sliding tap? Adjustable resistors © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What type of variable resistor is similar to a wire wound resistor? A potentiometer © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is a thermistor? A special type of resistor that can change resistance values as its temperature changes © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. Review What is a tolerance? The precision to which a value can vary © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only. For Discussion • What items other than an automobile could use a chassis as a conductor? • Discuss why a good understanding of the relationship among conductors, insulators, and semiconductors is important. © Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.