Which of the following is considered a hot or live wire in a circuit?

In electrical wiring, the designation of wire colors corresponds with their intended functionality in a circuit. A hot or live wire is one that carries electrical current from the power source to the device needing power. Typically, in many wiring systems, black wires are utilized as hot wires.

This standard is widely accepted in the United States, where black is often assigned to signify a wire that carries current. Meanwhile, other colors serve different purposes; for instance, red can frequently indicate a secondary hot wire or an auxiliary, blue can represent a traveler wire in a three-way switch setup or another type of control wire, and green is universally used as the ground wire, which is crucial for safety by providing an escape for excess electrical current.

Thus, among the choices provided, black is the conventional color identified as a hot wire, which underlines the importance of adhering to wiring standards for safety and proper function in electrical systems.