Why do some things come with polarized plugs when NO metal parts show?
Specifically, the powersupply brick for my Acer laptop (although it was bought later and did not come with the laptop).
It has nothing showing but plastic and maybe rubber. There are not even any screws to take the brick apart. But the plug is polarized!!
Why?
I would say so it fits the wall socket correctly. Even if it only has 2 prongs.
Wouldn't a non-polarized plug fit any wall socket?
The problem was that as usual when I go on a trip, I take an extension cord, but this time the power supply plug would not fit in the extension cord. With the few tools I had, I coudl not enlarge the slot in the extension cord. Fortunately, in the room I was renting, I soon found that it had a power strip next to the desk so I didn't need an extension cord, but that's because the normal tenant had changed and the new one put in the power strip, and the desk. I did need an extension cord the last two times I stayed in the very same room.
This was a two-prong plug for a universal laptop power supply.
I had also bougght a power supply just for the Acer, but I realized after I got it that the plug was 3 pronged, the cord was heavy, and the whole thing was too bulky and heavy** for traveling with, when the other one was lighter, witha 2-prong-plug
**And why did it need a 3-prong plug when there was no metal showing, only the cords and the plastic case with one little led peaking out. Not even any screws to take apart the case with.Is this required by some code, or is it overkill? I can't believe there is an electronic reason because it's alternating current, and unless some part of the circuit other than the plug could touch a ground or neutral, both wires are the same. The device doesn't know which input wire is hot and which is not, wrt the earth and the electric company.
I can't remember the last time I had an extension cord that wasn't polarized. While not all plugs are, *enough* are that I don't want to end up in a situation like you did. I'm not even sure I could find a 2 conductor extension cord lying around. A 3 prong cord fits just about every (US based) 120 VAC situation,
2 conductor plug or 3, polarized or not. Toss a 3 prong adaptor in your bag and you'll be ready for whatever (US based) 120 VAC situation you come across.I've made numerous extension cords from old PC power cords. They are really good cords and all it takes is a quality 3 wire connector and you've got a short extension cord that will probably last a lifetime.
Could be just standardization of parts.
Maybe non-polarized plugs are getting harder and harder to source by manufacturers, while polarized plugs can be purchased with ease.
or...
Whoever made the power supply you have probably makes other things with plugs, some (most?) of which require a polarized plug. Why keep 2 styles of plugs in inventory when 1 will fit every application?
The plug is polarized because the DC plug is polarized and if something goes wrong in the Power Supply it can not make the chassis of the laptop "hot" - or anything connected to the USB, or a keyboard or mouse - all of which are ALSO polarized. It's all part of the overall double safe or "double insulated" design
This one is 30 years old or more, but it's in good condition. Some have rubber that deteriorates, but not this one.
Yeah, but they are thicker, stiffer, and heavier, and when I travel I want lightweight and easy to fold and stuff in the suitcase.
This was Europe, 220V and a different style plug. I use a plug adapter** to switch to American parallel flat prongs, and then the extension cord. The extension cord has 3 outlets, one for the laptop, one for the phone charger, and one for the camera charger (when I used a separate camera. I may bring and use one next time too, or something else that must be plugged in. )
**So I only need one adapter this way, although I bring 3.PC power cords are 3-wire and they are thick, stiff, and per foot, heavy. Not really good for me. That they are short is not especially good. Sometimes in Europe there aren't as many receptacles as there are in most American housing, so I like having a long extension cord.
Maybe so.
Maybe so. (Your point is unchanged but fwiw, it would probably require
3 styles, because (not necessarily from the same company but power supply bricks in general) there are 3-conductor and two-conductor polarized.)Since no one has given a safety reason*** for a polarized plug in this case, I'm going to grind off some of the wide prong and make the plug unpolarized again. I've done this before but this time I wanted to check here first.
***I googled too and all the articles were basic or tangential to my question.
I answereed Mry. before reading this.
Hmmm. There are no metal parts showing in the laptop either, except the inside of the USB ports. But it seems to me there is already a 5v hot pin and a neutral pin in the USB port and if they get reversed, it would be no more dangerous than now.
and no metal parts showing in the mouse, keyboard, speakers, earbuds,
It sounds like it's "good practice" but with no particular advantage in this case.
Many years ago (say around 1940) some radios had the 'hot chassis' where the metal was connected to one side of the line. The polorised plug was needed. Later the radios did insulate the case from the chassis to eliminate some of the potential shock hazzard.
I just took inventory of my power tools with 2 prong plugs. Some are polorised and some are not. Being the 'double insulated' type there is no need to be polorised even it metal is on the outside like the drills. Interisting that several of the Harbor Freight tools are polorise and some of the others such as my Dewalt corded drill is not.
So they can use a SPST power switch and ensure that they're interrupting the current carrying conductor instead of the grounded conductor.
Assuming the receptacle is wired correctly.
Very often fused too. That is a very product specific device, which most manufacturers don't have any use for.
Yeah, good points. I just used my HFr drill this morning, to break up that ball of concrete in the woods near me. And I'm pretty sure it wasn't polarized. It has a metal chuck and a metal shaft leading to the chuck, but it's labeled double insulated so I'm sure it is.
BTW, OT, I've been using the wedges and feathers I got. I've broken the ball of concrete into 4 pieces (plus a few little pieces) and I think I have to go to 8 or 9 pieces to get them to be not heavy. But too hot/humid today to work more.
No, British 240V is still 1-Live, 1-Neutral, 1-Gnd, Single Phase
SOME are thick and stiff - but I have numerous flat Nema 5-15 to IEC320C13 cords as well as several Nema 5-15 to IECC20-C5 cords with very flexible flat profile and round profile cords - both AWG16 and AWG18. You will NOT want to use them on a space heater - or a coffee maker, or a laser printer!!!! They are generaly 6 or 8 feet long - Would be nice to have a device that plugs onto the IEC320 cord enf with multiple NEMA 5-15 outlets.
Usually 3A miniature fuses. Sometimes on both conductors.
Often 100-240V (including 100V for Japan).
I've heard of one product (LED fluorescent replacement) that's 100-277V.
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