When you look at the prongs on an AC power plug, there is always a hole punched in each prong. What is the purpose of these holes?
The holes in the prongs were originally developed by Nick Tezla Jr. who was employed as an engineer in the toaster division of the Sunbeam Corporation of Chicago in the 1930's. Sunbeam had recently lost several million-dollar lawsuits filed by consumers whose mouths were scalded by the napalm-like effect of Smucker's grape jam. This jam had been applied to toast which had come out of a Sunbeam toaster at an unreasonably hot temperature. Sunbeam management then asked him to come up with a quick fix for the 182,000 unsold toasters stored in a Cicero warehouse. Mr. Tezla, in a moment of inspiration, realized that if he could somehow impede the flow of electricity to the toaster, the ultimate temperature could be reduced.
Feverishly using his slide rule in the Sunbeam research laboratory one evening, he calculated that by merely punching one hole in each prong of the power plug, the electron flow would be impeded to the point where the toasters would run significantly cooler. He was so sure of his concept, that he immediately presented his idea to an executive session of the Sunbeam board of directors. They approved the modification of all the toasters in stock providing the cost was no more than 15 cents per toaster. All the other appliance manufacturers noted this change and applied it unthinkingly to their products without knowing the exact reasons.
There is footnote to this story with major implications. In the late 1980's, Sunbeam was concerned with price competition and found no good reason to continue with the process of punching holes in prongs in their appliances and ordered their prong-hole punchers dismissed. The cost savings resulted in Sunbeam winning the bid to be the sole source of the coffee brewers used in McDonald's restaurants in North America. You know the rest of the story.
Now, for my theory of why trailer parks attract tornados.....
(Thanks to Bill, KD0HG for passing on this tongue-in-cheek historical insight).