The Dangers of Missing Grounds on Plugs

What Does The Ground Do?

In every major commercial alternating current (AC) system, the power is transmitted through electrical lines, many which stretch high in the air. The possibility exists for dangerous potential voltages to form between the line itself and the ground (especially when a lightning strike imparts a huge amount of power to the earth or nearby power lines). Since many of these surges would be lethal, the addition of a ground line allows these dangerous potential voltages to bleed away harmlessly into the ground beneath your feet.

In a standard U.S. home, you receive a 240V alternating current power source. Large appliances use the entire 240V source, but smaller appliances require less. The main power is split into two equal 120V legs with a neutral return leg to keep the loads balanced. In the power plug, there are either two or three pins that connect to the openings in the wall socket. Generally, the smaller of the knife-like pins is called "hot" because it carries the alternating current from one of the two 120V legs. The other, larger, knife-like pin is called "neutral" because it connects to the neutral leg. If present, the third pin is called a "ground" because it is connected to a wire that is literally connected to the ground. This pin is larger than the rest of the pins to make sure you plug it in first so that the device is grounded before receiving power.

When you plug a power plug into a wall socket, you expose attached equipment to a potential spike of voltage. If the ground pin is not in place on the plug, that voltage spike has little place to go except into the component attached to it. Depending on the intensity of the voltage, the effect can range from a tiny spark to a life threatening explosion or fire. Even a harmless-looking spark can severely damage the sensitive electronics in devices such as computers and televisions. The ground pin also provides a measure of protection from voltage surges from lighting strikes during normal operation.

Though it is obvious to many people, it bears repeating that electricity can be dangerous. When you place a power plug into a socket, you are not only connecting an appliance to lethal levels of electrical current, but you are also making a potential connection between your body and the same dangerous power flow. If you use a power plug without the ground pin, the same electrical surges that can damage equipment can also electrify the outside of the equipment and harm you. During normal operation, the surface of an ungrounded appliance can also become conductive and provide a circuit to electrocute you. Given that normal AC current operates at a frequency that can literally cause your heart to stop, it is always wise to use properly grounded equipment.