What is a ground wire?
Tuesday, September 25, 2018
The electric cable that runs to the 120-volt outlets and other fixtures in your home has three wires inside the plastic sheathing: a hot wire (the “live” wire that brings the electricity in), a neutral wire (the one that routes the electricity back to the electric panel and completes the circuit), and a ground wire. The ground provides a safe, alternate route for electricity if it goes astray—perhaps because a hot wire has come loose at a connection or become frayed, and then comes in contact with the metal casing of a power tool or cabinet of a refrigerator, for example. Those parts are connected to the ground wire of the cord of the appliance and will complete a circuit whenever they become electrified.
Because the ground wire offers minimal resistance to the current flow, a surge of electricity will flow through it and trip a circuit breaker (or blow a fuse) in your electric panel and alert you to a problem. Without the ground wire connection, an electrically charged surface would do nothing, until you touch it while in contact with the ground or a grounded object, completing a circuit that would shock and possibly electrocute you.
A ground wire is bare (no insulation) or green. Electric outlets/receptacles have been required to have that third, round ground slot that connects to a ground wire since the early 1960s.
Also, see our blog post Why is it unsafe to bond neutral and ground wiring at subpanels?
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