Final answer:
Insulating materials such as polyethylene, PVC, and rubber are generally used to cover lines with less than 5,000 volts, offering high resistivity and protection against environmental factors and electrical charge transfer.
Step-by-step explanation:
Lines with less than 5,000 volts are generally covered with materials that serve as insulators, protecting the wires from environmental factors and preventing the accidental transfer of electrical charge. These insulating materials include various polymers like polyethylene, PVC, and rubber, which have high resistivity and are good at preventing the flow of electric current. In contrast, high-voltage power lines, such as a 240-kV transmission line carrying 5.00 × 10² A, use ceramic insulators hanging from grounded metal towers, each offering a high resistance of 1.00×10¹ ohms to support the effective transfer of energy over long distances. While aluminium or sometimes gold is used in wires to conduct electricity efficiently, the choice of insulation material for lower voltage lines is driven by cost, durability, and resistance to environmental factors such as corrosion.