View Full Version : Electrical Trivia Question-Looking For The Answer!!

Randy Meijer
07-06-2005, 9:59 PM
I've been looking at those little holes in the blades on electrical plugs for over half a century and never knew what they were for.....and I still don't?? Anybody have a clue........and please don't tell me that they help the electrons get into the wire!!:D

Rob Russell
07-06-2005, 10:24 PM
All I could ever think of is that they make it easy to lock a plug-in device out (so it can't be powered up). It's sort of tough to plug something in with a little padlock on the plug.

Doug Shepard
07-06-2005, 10:27 PM
I don't have a clue, but it's possible they're only there as a result of tooling holes left in the process of making them. They might not have any specific purpose.

Jamie Buxton
07-06-2005, 10:58 PM
The holes help to suppress the arc when you yank the plug out of the socket while a motor is running.

Rob Russell
07-07-2005, 7:41 AM
The holes help to suppress the arc when you yank the plug out of the socket while a motor is running.

How (curious)?

Larry Browning
07-07-2005, 8:13 AM
The holes help to suppress the arc when you yank the plug out of the socket while a motor is running.

Is this the actual engineering reason, or is it just your theory? That's a really good one. I always thought it was the lock theroy, but have never known the actual reason for the holes.

Lee DeRaud
07-07-2005, 9:20 AM
Well, as long as we're making up our own urban legends, here's mine:

The edges of the holes help scrape oxidation off the socket contacts as the plug is inserted, lowering the resistance of the connection.

That's as plausible as anything else I've seen here so far.:cool:

Dennis Peacock
07-07-2005, 9:46 AM
Well now....let me see........ :rolleyes:

The holes in the plugs are there to supress the arc when unplugging a device from the power source AND the holes are there to provide a type of heat dissipation to keep the prongs from over heating. :p :D


Jerry Clark
07-07-2005, 10:09 AM
Here is mine--:) The holes lock into indents on some type of wall receptacles to keep it from falling out. Don't ask which ones:cool: .

Randy Meijer
07-07-2005, 3:38 PM
I'm guessing that the guy who first designed the plug had a weird sense of humor and put the holes in for no other reason than to get guys like me to start threads like this???:D :D :D

Randy Meijer
07-07-2005, 4:37 PM
I just did an Internet search in hopes of finding an answer to this question. Turns out the answer to the question depends upon who you ask!!! Here is the most common response......with no guarantee as to its accuracy!!

<LI>If you were to take apart an outlet and look at the contact wipers that the prongs slide into, you would find that they have have bumps on them. These bumps fit into the holes so that the outlet can grip the plug’s prongs more firmly. This detenting prevents the plug from slipping out of the socket due to the weight of the plug and cord. It also improves the contact between the plug and the outlet.

<LI>Electrical devices can be "factory-sealed" or "locked-out" by the manufacturer or owner using a plastic tie or a small padlock that runs through one or both of the prong holes. Construction projects or industrial safety requirements may require this type of sealing. For example, a manufacturer might apply a plastic band through the hole and attach it to a tag that says, "You must do blah blah blah before plugging in this device." The user cannot plug in the device without removing the tag, so the user is sure to see the instructions.

There also is a small savings in raw materials (metal) for the manufacturer of the actual plug prong. Every little bit helps.....