Hell, I’ve even seen people rip them off to fit 3 prong plugs into 2 prong extension cords. I’m sure it’s not safe, but I dont know why and why they would be necessary sometimes and sometimes not.
The third prong is also usually longer than the hot and neutral prongs. That way when it is pulled out, the “earth” path is the last one to disconnect, maintaining the protective circuit until after the voltage is removed from the hot prong
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