Ground Wire

An intentionally grounded wire that completes a circuit if the neutral conductor fails. It's sometimes referred to as "earth" or "earthing" wire.

A bare or insulated conductor connected to the earth to create an electrical path of resistance for the purpose of conducting electrical current back to the ground.

In the US, this conductor is usually bare copper, or insulated as green, green/yellow, or black. The most typical and cost effective weather and abrasion resistant insulations are polyvinylchloride (PVC) and high molecular weight polyethylene (HMWPE).

Electrical circuits may be connected to the ground for several reasons. In powered equipment, exposed metal parts are connected to the ground to prevent contact with a dangerous voltage if the insulation fails. Connections to the ground limit the build-up of static electricity when handling flammable products or when repairing electronic devices.

In some telegraph and power transmission circuits, the earth itself is used as one conductor.

Please consult Article 250 of the most recent edition of the NEC for approved ratings in various applications. Final approval rests with your local electrical inspector.

Electrical current takes the shortest, most direct path to the ground. In your electrical circuits, the black wire (hot) supplies power, and the white wire (neutral) carries the current back. If the neutral wire is somehow broken or interrupted, well, you would be the electricity's direct path to the earth!

So the ground wire is like an insurance policy to carry the current back so you don't get shocked when the white wire fails. It also improves reception for listening and viewing quality.