Why are there Holes in the Prongs of Electrical Plugs? . Everyday objects often carry fascinating design details that go unnoticed. Among these is the ubiquitous electric plug, specifically the small holes in the prongs. If you’ve ever wondered, “Why do electric plugs have holes in the prongs?”, you’re not alone. This article dives into the practical, historical, and engineering reasons behind this seemingly minor feature.
Why Do Electric Plugs Have Holes in the Prongs?
As you may have already noticed the two little holes near each prong’s tip in an electric plug. If not, there are two holes mostly in Type-A (NEMA 1-15) and Type-B (NEMA 5-15) plugs which are commonly used in the US for residential and commercial applications. But did you ever think and wonder what are they for? If you are of this age to perceive with curiosity, let’s know what are the main purpose(s) of these tiny holes in the flat prongs of electric plugs?
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NEMA 1-15 (Type – A) plug with two flat parallel prongs was invented by Harvey Hubbell II in 1904-1906. NEMA 5-15 (Type – B) has the same two blades with an additional round (U) shaped prong used for grounding.
Reasons of Holes in the Prongs of Electric Plugs
- The indentations in the prongs in the first design by Harvey Hubbell II (and small holes later) was used as a safety feature. There were small bumps in the electrical outlets (receptacles and socket) which held the prongs tightly and firmly with the help of holes and indents in both plugs and outlets. These rightly fitted prongs would have not slipped back and pull-out easily. Additionally, the prongs with strong grip made perfect contact into the outlet’s slots.
- You may have heard about the Lock Out Tag Out (LOTO). As it was not the main intention because there was no concept of such things in the 1900s. But the manufacturer as well as the end user may use it now as a safety measure. For example, you may put a small lock or a plastic tag in the holes to prevent unauthorized operation of an electrical device and appliance. The same rule applies in homes for the safety of children.
- The manufacturer may consider that the holes in the prongs may save large metallic raw material based on large scale production.
- According to the official regulations by NEMA (National Electrical Manufacturers Association) and ANSI (American National Standards Institute), the holes in the pins and blades of electrical sockets are optional and intended for manufacturing purposes only. But you are free to use a padlock or plastic tag (or any other LOTO) to prevent your kids or any other unauthorized person from powering up certain appliances and devices. This may help to protect both the human and machines in unwanted and unpleasant conditions.
- Finally, the main reason for those holes in the prongs of power plugs was an old design with common use in the domestic and industrial applications for decades, the manufacturers now are not going to change the design that’s been around for almost 100 years. Same like the voltage level of 120V and 240V (or frequency of 60Hz) i.e. it won’t make sense with a new design of 99V AC (instead of 120V AC) or 40Hz frequency (instead of 60Hz or 50Hz) and so on.
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The Functional Role of Holes
Electrical Connection Efficiency : Holes in plug prongs serve to enhance the efficiency of electrical connections. Some outlets feature spring-loaded pins or other mechanisms that latch onto the holes. This improves the contact between the plug and outlet, ensuring a steady flow of electricity.
Secure Fit in Outlets : Another critical reason for the holes is to help the plug stay securely in place. When inserted, these holes allow locking mechanisms in certain outlets to grip the plug firmly, reducing the risk of accidental disconnection.
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Frequently Asked Questions
What is a 3 prong plug called?
What is a 2-prong plug called?
Which side of a 2-prong plug is positive?
What happens if the third prong breaks?
