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1. What are the types of common wires and cables classified by their uses? Answer: Based on their use, they can be classified into bare wires, insulated wires, heat-resistant wires, shielded wires, power cables, control cables, communication cables, RF cables, etc. 2. What are the types of insulated wires? Answer: The common types of insulated wires include: polyvinyl chloride insulated wires, polyvinyl chloride insulated flexible wires, nitrile-polyvinyl chloride mixture insulated flexible wires, rubber-insulated wires, aluminum-core plastic-insulated wires for underground use in agriculture, rubber-insulated cotton yarn textile flexible wires, polyvinyl chloride insulated wires with nylon sheaths, and polyvinyl chloride insulated flexible wires for power and lighting applications. 3. In what situations are cable trays suitable? Answer: Cable trays are suitable for the overhead installation of power cables and control cables in indoor and outdoor areas of general industrial and mining enterprises; they can also be used in sectors such as telecommunications and radio and television for similar purposes. 4. What are the cable accessories? Answer: Common electrical accessories include cable terminal junction boxes, cable intermediate junction boxes, connection pipes and terminals, steel plate wiring troughs, cable trays, etc. 5. What is a cable intermediate joint? Answer: A device that connects the conductors, insulation shielding layers, and protective layers of cables together to enable the connection of cable circuits is called a cable splice. 6. What is the main electrical wiring? Answer: The electrical main wiring is the method of connecting the main electrical equipment and busbars in power plants and substations, including the connection between the main busbars and the plant service system according to specific functional requirements. 7. What regulations should be followed when selecting the cross-sectional area of power cables? Answer: The selection of power cables should follow these principles: (1) The rated voltage of the cable must be greater than or equal to the rated voltage of the power supply system at the installation site ； (2) The continuous allowable current of the cable shall be equal to or greater than the maximum continuous current of the powered load ； (3) The cross-sectional area of the conductor core must meet the stability requirements in the event of a short circuit in the power supply system ； (4) Check whether the voltage drop meets the requirements based on the cable length ； (5) The minimum short-circuit current at the end of the line shall be sufficient to ensure reliable operation of the protective devices. 8. What are the advantages of cross-linked polyethylene cables compared to oil-paper cables? Answer: (1) It is easy to install, as it allows for a small minimum bending radius and is lightweight ； (2) Not restricted by line elevation differences ； (3) Good thermal performance, allowing high operating temperatures and large transmission capacity ； (4) The cable accessories are simple, all being of dry-type design ； (5) Simple operation and maintenance, with no oil leakage issues ； (6) Lower price ； (7) High reliability and low failure rate ； (8) It has few manufacturing steps and a simple process, resulting in significant economic benefits. 9. What are the requirements for the clamps used to fix single-core AC cables? Why? Answer: The fixture should not contain any iron components that could form a closed magnetic circuit. This is because when current flows through the cable core, magnetic field lines are generated around it, and the strength of these magnetic field lines is proportional to the magnitude of the current flowing through the core. If magnetic conductive materials such as iron are used, electromagnetic induction dictates that eddy currents will be generated in those materials, causing the cable to heat up and even getting it damaged. Therefore, iron components cannot be used as fixing clamps for single-core AC cables. 10. What are the main features and advantages of the accessories for the following heat-shrinkable cable terminals? Answer: The main advantage of heat-shrinkable fittings is the use of stress tubes in place of traditional stress cones. This not only simplifies the installation process but also reduces the size of the joint ends. They are easy to install, save time and labor, offer superior performance, and help conserve metal. The heat-shrinkable cable accessories combine the poured and dry-pack types, integrating the advantages of both types of accessories.