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[YouTube]: American is impressed by sensible British mains plug design

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IanB:

--- Quote from: PlainName on October 23, 2022, 02:57:31 pm ---What are the holes in the US prongs for? Are they for ball bearings to drop in and retain the plug? I presume they're not so some kid can bolt some wires to them...

If they are part of a retaining mechanism, shouldn't that mitigate against them falling out of the socket, but still allow them to pop out if the cable is snagged?

--- End quote ---

A long time ago, receptacles were made with a protruding nub on the spring that latched into the hole and made the plug more secure. But things changed and receptacles today are made with much stronger spring force and no longer need that feature. However, plugs are still made with the holes in the prongs, just in case they get plugged into one of the older receptacles that was made with the locking nubs inside it.

PlainName:
Thanks :)

IanB:

--- Quote from: coppice on October 23, 2022, 02:21:14 pm ---There have long been some niche products like that. You made it sounds like bayonet lamps are safe. The vast majority are not.

--- End quote ---

To be practical about it, if you poke your finger inside a bayonet socket while it is switched on, the most likely outcome is that your finger will contact both pins at the same time. So the result will be that your finger gets zapped, which while painful, is not dangerous. Realistically, the probability of receiving a shock current that goes through your heart is low.

We can also observe that every child over the age of 4 or so knows not to poke fingers in light sockets. And children under the age of 4 need to be supervised and have all kinds of dangerous things kept out of reach.

While there is an undeniable possibility of electric shock, it is an exaggeration to say that such light sockets are not safe. There are countless millions of them installed and there is a negligible incidence of harm arising from them.

TimFox:

--- Quote from: PlainName on October 23, 2022, 02:57:31 pm ---What are the holes in the US prongs for? Are they for ball bearings to drop in and retain the plug? I presume they're not so some kid can bolt some wires to them...

If they are part of a retaining mechanism, shouldn't that mitigate against them falling out of the socket, but still allow them to pop out if the cable is snagged?

--- End quote ---

I don't know the original design requirement, but I have seen small padlocks inserted through the two flat-blade holes to prevent installation.

TimFox:

--- Quote from: Halcyon on October 23, 2022, 10:13:09 am ---
--- Quote from: Monkeh on October 20, 2022, 02:15:48 pm ---
This is precisely why strain reliefs fail, and is a practice which encourages unnecessary wear and tear and increases the chance of a fault in the plug or socket.
--- End quote ---

Yeh, maybe. But in my time, I've never actually seen a plug fail in this manner. They are extremely robust. That's not to say it doesn't occur, but it's rare.

A clean, low (physical) resistance break is far less likely to result in damage to a plug or socket. Even if it's unintentional (like you moving a vacuum cleaner just that bit too far), I'd rather just have it shut off because the plug was pulled as opposed to damaging pins or the wall socket itself.

--- End quote ---

Perhaps the extreme example in current use of a high physical resistance break is the US series of "twist lock" connectors, mostly used in industrial or commercial contexts for single or three-phase cordage. 
https://www.hubbell.com/wiringdevice-kellems/en/Products/Electrical-Electronic/Wiring-Devices/Locking-Devices/Insulgrip-Twist-Lock/c/2027741
Even if you drive away in your pickup truck with the compressor in the back still plugged in, you can't pull the mating connectors apart, but the cord on one end of the mated pair will fail, possibly exposing live wires.

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