What is the primary purpose of the third wire in a cable installation?

The primary purpose of the third wire in a cable installation is typically to serve as a ground wire. Grounding provides a critical safety feature in electrical systems by creating a path for fault current to safely dissipate into the earth. This helps to prevent electrical shock hazards by ensuring that any fault is directed away from users.

In many electrical systems, grounding is crucial because it protects equipment and reduces the risk of electrical fires caused by short circuits. The ground wire may also help stabilize voltage levels for electrical systems and prevent damage to appliances due to voltage spikes.

While a neutral wire is essential in completing circuits by providing a return path for current, it does not serve the specific safety role that a ground wire does. On the other hand, a live wire, or hot wire, carries the current to the electrical device. Thus, in the context of safety and protection, the function of the ground wire is paramount, confirming that it is the most accurate answer.