This article describes the difference between the functions of the neutral wire and ground wire in residential electrical circuits.
If you have ever peeked inside the service panel (if you haven't, please don't), where the electricity enters your house, you might have noticed that the neutral wire (which has white insulation) and the ground wire (which has green insulation or is bare copper or aluminum), are connected to the same grounding bar. So what's the difference? Why do two different wires go to the same place?
Before I describe the different functions of a neutral wire and a ground wire, I'll provide a brief general description of how residential electrical systems work, starting with a couple of definitions: voltage refers to the amount of pressure of electricity in a circuit; amps refers to the rate at which the electricity moves through the wire.
Electrical current comes into your home through the service panel, a gray box somewhere in your basement or utility closet. From there, the electricity is distributed through several circuits in your home. The cable usually consists of three wires: hot (black or sometimes red), neutral (white), and ground (bare copper). The hot wire conducts the voltage (electricity under pressure) from the service panel to the appliance or fixture. Because electricity always seeks ground, after it is used it flows back through the neutral wires to the grounding bar in the service panel (but not under pressure).
So what purpose does the ground wire serve? It provides a path back to the service panel for short circuits. Without a ground wire, if a neutral wire came loose somewhere in a circuit, the electricity would have no path back to the service panel. In fact, the electricity would probably use the first person it came in contact with as a path back to ground.
So, whereas the neutral wire conducts electricity back to the service panel under normal conditions, the ground wire is there to conduct the electricity back to the service panel in case something goes wrong (like a short circuit).
Because the ground wire plays such an important role in the wiring circuit, you should never remove the ground prong from three-prong plugs. If there is a short circuit in the appliance you're using, the ground prong allows the electricity a path back to earth.
Also, do not replace two-prong outlets with three-prong outlets without grounding the new outlets. It wouldn't hurt to check the outlets in your house to ensure that they are grounded. You can do this with an outlet tester (pictured), available in any hardware store. You simply plug the tester into the outlet, and lights indicate correct or incorrect wiring. If the wiring is incorrect, see the warning below.
What article on electricity would be complete without the usual caveat? The purpose of this article is to describe the differences between the ground and neutral wires. It is not intended as a guide for actual work performed. If you need to have some wiring done in your house, I recommend hiring a professional.