Types of Circuits - Grounded Circuits
Have you ever touched an electrical appliance and felt a shock? It probably was an un-grounded device. And, you certainly have been warned about touching electrical appliances when your feet or hands are wet. While not common a few decades ago, almost all household equipment today is grounded with a round third prong, and there are even detectors in modern bathroom electrical systems that detect and interrupt circuits whenever even a small amount of current is flowing through that ground. These devices are called ground fault circuit interrupters of GFCIs. See the Safety section for more information on grounding and GFCIs.
Grounding is achieved in an electrical system when one of the conductive wires serving as part of the circuit path is intentionally given a direct path to the earth. This is commonly accomplished by connecting one of the circuit wires to the soil or ground by running a wire to a ground rod, a long copper rod driven directly into the soil.
Advantages of grounding one wire of a circuit include safety and reliability. Without grounding, both wires are "hot," meaning the wires are energized at the circuit voltage. If someone touched the conductive part of either wire, they would be exposed to the full circuit voltage. With a grounded circuit, only one wire becomes hot and the other wire is grounded. Touching the hot wire still exposes a person to the full circuit voltage.
In a grounded circuit, we often refer to the electricity traveling from the source to the load on the hot wire and returning to the source on the grounded wire. This is not quite correct since AC current changes direction 60 times a second.
Electrical power suppliers also commonly ground one of the wires on the electrical distribution system by connecting it to the ground. This is done by running a copper wire from a clamp around the wire to a ground rod at the bottom of the pole. This "grounded" wire has several different names including the neutral wire, and grounded neutral wire.
Grounding electrical utility distribution circuits is also done for safety and reliability reasons on the electrical system. If the electric system was not grounded, lightning would follow the path of the wires either through the customer's appliances or the utility's wires to the generator.
Remember, electrical system grounding is not the same as electrical equipment grounding. Electrical equipment is grounded using a third wire run to an appliance or device and connected to the third "round prong" of the outlet.