I have a 2.5 year old grandson I moved across the country to take care of and my daughter and I collide with what is safe to allow for him to do and not do..... For instance he likes to plug his light in and I tell him to ask for help and he does when he's with me but as soon as mama comes home he's plugging in the cord by him self..... She says it's one less thing for her to have to do?? Maybe I'm in the Stone Age and things have changed my daughter and son in law just laugh at me and say he will only get zapped once then he will know better...... Should I just let it go or is there anything to be concerned about? From a concerned grandma
I think you have to distinguish three points:
Depending on your country and the used connector types, it may be possible to touch mains voltage while plugging in.
When pushing the connector into the plug, the pins will touch the contacts carrying mains voltage at some point where the connector is not yet fully plugged in. It may still be possible to touch the pins, especially with the tiny fingers of a small child. This is dangerous. (Another danger: It's possible to push a thin wire, a piece of aluminum foil or similar between outlet and the plugged-in connector, and so to touch mains voltage.)
The UK uses this connector type, and a flat outlet similar to that of the US:
Here, the shaft of the pins is insulated (black plastic) and only the tip is made of metal. The pins will touch the contacts at a point when the entire metal part is already fully inserted into the hole of the plug. It's not possible to touch them any more at this point, which makes it safe. I'm not sure if the pins have always been insulated, ancient connectors may have pins entirely of metal, which are not safe.
May be an other example. The so-called Schuko connector, used in Germany and several other European countries. Schuko doesn't have plastic insulation, but the shape of the outlet ensures you can not touch the pins when inserting the plug:
Finally, this three examples show the problems and two ways to avoid them, and it should be possible to judge if any other connector type is safe or not. From the technical side, I don't think I would allow a small child to plug in a connector in the US, while I have no concern in Germany / UK.
(And a comment: These connectors have two pins for "current in" and "out" and one pin/contact for protective earth. The latter doesn't carry voltage on it's own, so the problem of touching doesn't apply for it.)
When I was a small child, I watched my grandfather drilling a hole into the wall. Later on, I wanted to do so, too. As the knitting needle didn't well on the wall, I tried one of that "pre-installed holes", but for luck got the "current return" hole without voltage.
Today, there are tamper-resistant outlets which close the holes by a piece of plastic from inside. Only, when you try to insert something into two (or three) holes at the same time, they open. So, this prevents small handymen from inserting stuff. But you have to check if your outlets have this protection. (Mandatory for new installations in US/Canada since 2008/2009!)
The child itself
The child knows from the adults that it's normal to put things into outlets all day. This makes it curious about that holes in the wall, and it may want to try other things. So, if you forbid to plug the cord in, this may increase curiosity, but if you allow or encourage the child to do it, you point it to this holes.
I'm not sure what to advise here, as I'm more on the technical side. And as the parents already allowed it, it's a bit late to think about this point.
Finally, a child should be teached to handle plugs and outlets responsibly and with the necessary respect. But... at age of 2.5?
...will only get zapped once then he will know better
May be, he won't be able to know better or do again! Mains voltage is dangerous and can kill you! In most cases, people touching mains voltage manage to pull away their fingers quickly and only get a painful zap, but often enough, they get electrocuted. Even if it was only a zap, it is often advised to go to the hospital, as a zap could cause a cardiac arrest within 24 hours.
So, when it's so dangerous for adults, how dangerous is it for a small child?
My answer would be absolutely no (I am in the USA), but as gramma I am not sure what you can do about that. I know of a local baby that drooled onto a power strip & was significantly zapped in the face to the point of needing a muscle graft. I also zapped myself once & while I am okay, it was highly unpleasant & caused me a temporary arrhythmia. I am an artist. I had a easel that used to hang on a wall with an overhead light. I went in at night to discover the overhead was burned out. I also managed to have no flashlight batteries (young people problems) so I grabbed a lamp from another room knowing where there was a socket, assuming I could feel my way in the dark. I would have been fine, but I was bracing one hand on the wall while plugging in with the other. The hand on the wall happened to be on a chain that connected the front two legs of my easel to the back leg. I managed to catch that same chain between the plug pegs, so when I plugged it in, the whole chain glowed, it zapped the heck out of me & left soot streaks up my wall. It also managed to fry the lamp in the process. Mind you this was on a grounded line, but the lamp had 2 prongs, not three, as most still do. Thank goodness I blew a fuse as I wasn't able to move myself. My arrhythmia came back on & off for a few years after. Eventually I was on a medication to regulate rhythm & then later weaned off from it & that seemed to work finally. It wasn't a minor thing for me at all.
So no...you would not catch me allowing a child that age anywhere near it. In fact, for my kids I have installed all sorts of safeties to ensure they do not have any access to plugs at all. Mine have covers that lock in & allow you to plug in & then lock over the plugs. I then have long straight plastic conduit that covers my cords and attached to the wall because a child can pull hard enough on a weaker cord to detach it from the head, as I figured out. It's no danger to the child, but not fun to remove. Not all of my lines can be wall mounted of course, such as kitchen appliances, but those are all high enough to be out of reach anyway. They still have safety covers when not in use though, in case. Feeling your heart go all wonky for a few hours after a good solid jolt isn't something I take lightly and then having linger issues was very worrisome & I won't chance my child having it happen. You will likely be fine, as I was eventually, or you can stop your heart or go into a fatal arrhythmia, or or or. I am not taking that chance with kids.
To me saying "he will only jolt himself once" is like saying a kid will stay out of the street if they get hit. In cases like this, you are supposed to have the child be old enough to grasp the danger so you can teach safety before the kid gets zapped. At 2.5yrs, I've yet to know a child capable of understanding that level of risk or any risk really. In fact, at 2.5yrs, most of my kids would have happily walked into the street if I hadn't stopped them 100's times. This is an age where they will walk up to a dog they have never seen & slap it in the face or poke an eye, wander into traffic, step off into the deep end of a pool, cram anything small enough into their mouths or up the nose, hit your window with a hard object, etc and have absolutely no clue what is going to happen next. They just do not grasp how life works. Every one of my kids at this age has eaten something they found on the ground/floor when out in public. If they threw up later they had no clue it was likely that nasty thing they ate a few hours ago, so when they find that next treat, they'd eat it again I am sure if I didn't catch them first. So I can't fathom thinking they can handle plugs. I am aware other countries have different outlets & if that were the case, perhaps I'd feel differently. I know that what is in my home isn't suitable for small kids, even with the standard "safety" features. And I can't understand the idea of "one less thing to do" because in all the things I do in a day while parenting, plugging things in has never been work to me. Now if you can get that kid sweeping, scrubbing, doing laundry, picking up after himself & putting all toys away, more power to you. That would be awesome. Plugging things in isn't something we do often around here so I can't imagine why it's a hassle to do it yourself or why you need to do it all the time.
And just to be clear, I don't think it's "bad parenting", even if in the USA. I would think it's perhaps naive about what a zap can be like & not understanding the actual implications of it fully. If someone had actually been zapped like I was, they wouldn't ever think to let their toddler be at any risk of experiencing it. I let my kids climb trees & do all sorts of exploring & typical kid risk taking & they do get hurt sometimes. That stuff is totally within normal kid life & part of learning one's limits. I don't take chances on things that they don't need to be doing though and this would be one of the things they don't need to do, at least not at this age.