For non-metallic cable, which wire is connected to the outlet box?

The connection of wires in a non-metallic cable (commonly known as Romex) typically follows a standard color code which is essential for safety and proper function in electrical systems. In this context, the use of bare copper wire is specifically meant for grounding purposes. For outlet boxes, grounding is a crucial component to prevent electrical shock and to facilitate the operation of safety devices like circuit breakers.

Bare copper wire serves as the ground wire and is connected to the outlet box to provide a safe path for electricity in case of a fault or short circuit. It helps to redirect excess electrical current into the ground, minimizing the risk of electrical hazards. Grounding also reinforces the safety of any device connected to the outlet by ensuring that there is a direct route for errant electricity.

In contrast, the white wire typically serves as the neutral conductor, while the red and black wires are generally used as hot wires in different circuits. These wires fulfill different roles and do not provide the grounding function that is essential for safety in electrical installations. Hence, connecting the bare copper wire to the outlet box is the correct practice in ensuring safety and compliance with electrical codes.