I asked a retired engineer that worked for GE this question a long time ago.
I was 18 and he was about 65 at the time. His answer was a little different
from the howstuffwprks answer. He gave the same discription of the socket
but said it improved the electrical connection instead of holding the plug
in the socket better. It allowed the bump to contact the plug over a larger
area. After thinking about it the design probably does both. Just think a
bump touching a flat blade or a bump fiting down in a hole. which is going
to have the largest area of contact.
The Straight Dope addressed this question, and there seems to be no one simple
Just for the record, I just dismantled two outlets, one inexpensive one and the
other a high end commercial quality Decora... no dimpled tab in either, just
flat copper strips.
On Fri, 07 Mar 2008 13:14:33 -0600, snipped-for-privacy@SPAMwowway.com (DT)
I think it's because putting holes in things make them stronger, like
the guy said. Look at the George Washington Bridge in NYC. It has
loads of holes and look at how strong it is.
I have a related question. Why are some prongs solid, others are
folded over with each layer totally flat against the other, and still
others are foled over but have one side freely attached and springy.
The third kinds seems the best.
But sometimes with the second type, I force the two layers apart so
the plug will stay in the outlet better.
Why don't they make this easier to do?
Will I cut my finger off?
The straight dope piece seems to have gotten it right - about
it _used_ to be necessary with old outlets that didn't grip so well,
the pins could interlock into buttons on the tabs. So, it used to have
a reason, and now it's probably they can't figure out why they're
there, so it's easier to stay that way ;-)
Punching holes in metal structures does not make them stronger. In
fact, it makes them somewhat weaker than equivalently sized solid
structures. The reason punching holes (or leaving it out altogether
such as in trusses) it is to make it _lighter_.
They're aiming for the rigidity implied by the larger cross-section,
without some of the added weight.
The only ones of the third kind I've seen have been folded types that
wore so badly that the join (at the tip) is gone. Or were clipped.
The temptation for one to go sideways is too high.
As to why some are folded and some are solid - different manufacturing
Age and Treachery will Triumph over Youth and Skill
come on now, lets tell alan the truth...it's so you can
snip off the grounding plug, and then its easier to snip
through the blade, cause it's usually the larger one, then
you can plug it into a 2 prong nongrounded plug........
Also if the device being powered is shorted, when you insert the plug into
an outlet, the narrower conductor around the hole tends to melt off (pow!)
before you can insert the plug all the way. I don't know that this is by
design, but it is a beneficial aspect.
I always figgered those holes were there so that in a pinch you could
make an erzatz extension cord out of a length of 14 gage Romex.
The holes in the plug blades makes it easier to crimp the stripped solid
wires onto them, and then you just make narrow U-bends in the stripped
other ends, pound them flat, and jam them into the two slots of a
Jeff (Never believe everything I say <G>)
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.