Which type of conductor is described as a general-purpose single conductor for installation in conduit?

The correct choice is a type of conductor known for its versatility and is widely used in various electrical installations, particularly in conduit systems. THHN (Thermoplastic High-Heat Resistant Nylon-coated) wire is specifically designed for use in dry locations and is suitable for general-purpose applications. It features a thermoplastic insulation that is suitable for high heat environments, making it ideal for use in conduit installations where it can be protected from physical damage.

This type of conductor is often used in commercial and residential applications, facilitating both power distribution and connections within electrical systems. THHN is known for its durability and ability to handle high voltage, which makes it a reliable choice. Its availability in various gauges also allows for flexibility depending on the requirements of the installation.

While UF-B, SE-R, and XHHW are all legitimate types of conductors, they serve different purposes. For example, UF-B is suitable for underground applications, SE-R is typically used for service entrance applications, and XHHW is designed for wet locations and has different insulation characteristics. Therefore, THHN stands out as the general-purpose option particularly suited for installations in conduit.