LEARNING OBJECTIVES
Learning objectives are stated at the beginning of each chapter. These learning objectives serve as a preview of the information you are expected to learn in the chapter. The comprehensive check questions
are based on the objectives. By successfully completing the OCC-ECC, you indicate that you have met the objectives and have learned the information. The learning objectives are listed below.
Upon completing this chapter, you should be able to:
1. Recall the definitions of unit size, mil-foot, square mil, and circular mil and the mathematical
equations and calculations for each.
2. Define specific resistance and recall the three factors used to calculate it in ohms.
3. Describe the proper use of the American Wire Gauge when making wire measurements.
4. Recall the factors required in selecting proper size wire.
5. State the advantages and disadvantages of copper or aluminum as conductors.
6. Define insulation resistance and dielectric strength including how the dielectric strength of an
insulator is determined.
7. Identify the safety precautions to be taken when working with insulating materials.
8. Recall the most common insulators used for extremely high voltages.
9. State the type of conductor protection normally used for shipboard wiring.
10. Recall the design and use of coaxial cable.
Introduction to Electrical Conductors, Wiring Techniques, and Schematic Reading
Electrical conductors, wiring techniques, and schematic reading are fundamental topics in electrical engineering and practical applications. They form the basis for designing, constructing, and troubleshooting electrical circuits, making them essential for anyone working with electrical systems.
1. Electrical Conductors
Electrical conductors are materials that allow the free flow of electric current due to their low resistance. The ability of a material to conduct electricity depends on its atomic structure, particularly the availability of free electrons.
Common Conductive Materials:
- Copper: The most widely used conductor in electrical wiring because of its excellent conductivity, flexibility, and resistance to corrosion. It is the standard material for residential, commercial, and industrial wiring.
- Aluminum: Lighter and less expensive than copper but with lower conductivity. It is often used in power transmission lines and some building wiring, particularly for large conductors.
- Gold and Silver: While they have higher conductivity than copper, their high cost limits their use to specialized applications, such as high-performance electronics and connectors.
- Other Conductors: Materials like carbon, steel, and specific alloys are used in applications where specific properties like strength or temperature resistance are needed.
Insulating Materials: Electrical conductors are typically covered with insulating materials such as PVC (polyvinyl chloride), rubber, or Teflon to prevent accidental contact, short circuits, and safety hazards.
Types of Electrical Conductors:
- Solid Wire: Consists of a single solid strand of metal. It is durable and ideal for permanent installations but less flexible than stranded wire.
- Stranded Wire: Made up of many small strands twisted together. It offers greater flexibility and is commonly used in applications where the wire needs to bend or move frequently, such as in extension cords.
- Cable: Refers to a group of insulated wires bundled together. Examples include coaxial cables, multi-core cables, and power cables.
2. Wiring Techniques
Wiring techniques involve the proper selection, installation, and connection of conductors to ensure a safe, reliable, and efficient electrical system. Proper wiring is crucial to prevent faults, reduce energy losses, and enhance system performance.
Key Wiring Techniques:
- Color Coding: Wires are color-coded based on their function to simplify installation and maintenance. For example:
- Black/Red (Hot/Live): Carries the current to the load.
- White (Neutral): Returns the current to the source.
- Green/Bare Copper (Ground): Provides a path to the ground to prevent electrical shock.
- Soldering and Crimping: These techniques are used to make secure and reliable electrical connections. Soldering uses a metal alloy to join wires, while crimping involves compressing a connector onto a wire.
- Wire Splicing: The process of connecting two wires by twisting them together and covering them with a wire nut or electrical tape. This method is used in junction boxes to extend or branch circuits.
- Cable Management: The practice of organizing and securing cables using clips, ties, conduits, or trays to prevent tangling, damage, and electrical hazards.
- Conduit Wiring: Wires are run through protective metal or plastic tubes called conduits. This method provides additional protection against physical damage and is commonly used in industrial and commercial buildings.
Types of Electrical Wiring Systems:
- Residential Wiring: Typically uses non-metallic (NM) cables, such as Romex, for general household wiring. These cables have two or more conductors inside a plastic sheath.
- Commercial Wiring: Often uses metal-clad (MC) cables or conduit systems to provide additional protection in environments where wires are more exposed to damage.
- Industrial Wiring: Utilizes robust, high-capacity conductors and complex wiring techniques to handle large loads and harsh environmental conditions.
Safety in Wiring:
- Properly ground all electrical systems to prevent electrical shocks.
- Follow local electrical codes and regulations to ensure compliance with safety standards.
- Use appropriately rated wires and connectors based on the current load and voltage requirements of the circuit.
3. Schematic Reading
Schematic reading involves interpreting electrical diagrams that represent the components and connections in a circuit. Schematics are essential tools for understanding, designing, and troubleshooting electrical systems.
Basic Elements of a Schematic Diagram:
- Symbols: Standardized symbols are used to represent different electrical components. For example:
- Resistor: A zigzag line
- Capacitor: Parallel lines (one line may be curved for polarized capacitors)
- Inductor: A series of loops or a coiled line
- Diode: A triangle pointing to a line, indicating the direction of current flow
- Transistor: Symbols vary based on type (NPN, PNP), showing three leads (collector, base, emitter)
- Switch: An open or closed line indicating an ON/OFF position
- Lines and Connections: Straight lines represent conductive paths (wires) between components. A dot at the intersection of lines indicates an electrical connection (node).
- Power Sources: Batteries, DC power supplies, or AC sources are depicted by specific symbols showing their polarity and type.
- Ground Symbol: Indicates the reference point for the circuit's voltage, often connected to the earth or chassis ground.
Steps to Read a Schematic Diagram:
- Identify the Power Source: Locate the power supply and determine the voltage levels used in the circuit.
- Trace the Current Path: Follow the current flow from the power source through the components and back to the ground or return line.
- Understand Component Functions: Analyze each component based on its symbol and understand its role in the circuit, such as providing resistance, storing energy, or switching current.
- Look for Control Elements: Identify switches, relays, or transistors that control the flow of current in the circuit.
- Analyze Connections: Check the connections between components to understand how they interact and influence the overall circuit behavior.
Common Types of Diagrams:
- Wiring Diagrams: Show the physical connections and layout of an electrical system, often used in building wiring and automotive applications.
- Block Diagrams: Provide a high-level view of a system, showing major components and their interactions without detailed circuitry.
- Pictorial Diagrams: Represent electrical components in a more realistic way, showing the physical appearance of components rather than standardized symbols.
4. Integration of Conductors, Wiring Techniques, and Schematic Reading
In any electrical project, these three elements are closely integrated:
- Selection of Conductors: Based on the electrical requirements, suitable conductors are chosen for wiring the circuit.
- Implementation of Wiring Techniques: Proper wiring techniques are applied to ensure safe and reliable connections, with attention to factors like insulation, grounding, and cable management.
- Reading and Creating Schematics: Schematic diagrams are used to plan the wiring layout, guide installation, and assist in troubleshooting. Understanding these diagrams is essential for following proper wiring techniques and ensuring correct connections.
Conclusion
Electrical conductors, wiring techniques, and schematic reading are fundamental skills in the electrical field. Conductors form the pathways for electric current, wiring techniques ensure safe and reliable installations, and schematic reading provides a blueprint for understanding and building electrical circuits. Mastery of these concepts is crucial for anyone involved in electrical design, maintenance, and troubleshooting, as they form the foundation for efficient and safe electrical systems.
