What's that copper wire hanging down from our light?

We recently replaced our dining room light.. it looks great, thanks for asking! During this process I noticed a wire that the designer in me wanted gone. So why is it there and what is it?

Ben, what is that copper looking wire hanging from our light?

That's the ground wire and it's there for your safety.  Lighting fixtures (as well as any appliance with a metallic chassis or housing) have three wires: one that's black, one that's white and one that's either green or bare.  The black wire is Hot, which means that it has 120VAC on it.  Don't touch that one.  The white wire is Neutral which is the return path for the circuit in question and it is at ground potential, which means there isn't any voltage on it.  The green or bare copper wire is the ground wire which is attached to the metal enclosure and is connected to ground.


Without a ground wire, if the black wire comes loose and touches the metal enclosure, then the whole enclosure is sitting at 120 volts so if you touch it you get a new hairdo.  However, if you properly connect the ground wire then if the black wire touches the (now grounded) metal enclosure, then the grounding wire creates a short circuit to ground which will trip the breaker so that there is no shock hazard.  It's not as exciting, but nobody dies so it's sort of a tradeoff.