That third prong on your extension cord plug (and appliance cords), enables electricity to flow through the circuit and then, literally, into the ground. It makes electrical systems safer because electricity can flow into the ground rather than through you if there is a short circuit. It can prevent fires and electrical shocks.
According to electrical codes, all structures are required to have the electrical system connected to a metal grounding rod. The metal rod gets driven 8 feet into the ground (in the soil outside the house). The grounding rod must be deep in the ground because we want to make sure that there is a way for stray electricity to be dissipated into the ground.
In 1971, all electrical outlets and other electrical circuits were required to be grounded. This was a major step in the right direction for electrical safety. In addition, Ground Fault Circuit Interrupters (GFCIs) started to be required in all new construction. Eventually, GFCIs became required in all “wet locations” including garages, exterior outlets, bathrooms, kitchens and basements. GFCI outlets shut themselves off immediately if there is an electrical leak through the grounding system. GFCIs save lives!
The good news is, that the world has become safer due to better grounding systems and electrical safety devices.
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