That doesn't make sense though. The fuses aren't to protect the load; they are to protect the circuit. It's up to whatever device you are plugging in to not draw more current than it can handle.

If I have a 3 Watt doohickey, I don't go looking around to find a 0.025A socket, I plug it in to my 15A wall socket and everything works great.

Yeah, the risks mainly come with extension cords, like plugging a bunch of 10A appliances into a single 20A outlet via a 10A rated extension cord with multiple 10A outlets.

Appliances themselves with their own input fuses and captive cables are less risky, although some kind of internal wiring short could still get all melty.

It's true that sizing the plugs that way does prevent you from plugging a 20A appliance into a 10A extension cord, which makes sense.

Each individual socket isn’t fused though. The entire circuit is. The fuse(breaker) is going to be significantly bigger than any of those amperages.

The breaker is there to protect the wiring in the building, nothing more. It’s spec’d to the gauge of the cable in the wall typically.

It's not dangerous in practice. Reading through NEC in the US, there's plenty of leeway for mixing ampacity ratings on circuits, within certain limits. For example, it's fine to have 10x 15A duplex on a 20A circuit. It results in less wiring, and allows for logical grouping of circuits. Electrical code starts from the the most common causes of electrical failures, and tries to design down from there. The ampacity ratings on devices and various components of the circuit are designed to reject the common causes of failure, and conductor failure at the device isn't one of them (appliance manufacturers are more likely to get their devices certified, so if there's a failure in the appliance, some other part of the appliance's electrical system will fail before the conductors do).

So the ampacity of the connector (duplex and plug) is meant to reject certain combinations (plugging a 30amp appliance into a 15amp duplex/circuit). It's obviously very easy to get around that by just wiring things together wrong (18AWG wire on a 30Amp circuit), but by design, a 30amp appliance with the proper plug cannot be plugged into a 15amp outlet.

Of course, this is informed by the electrical code in my home country, so I understand that other places and people have different experiences, but electrical accidents have been on a steady downward trend since the 80's, so the NFPA NEC has to be doing at least some things right.

It is indeed very regional, e.g. the UK has its own thing going on with ring mains and fused plugs.

Over in my 230V corner of the EU, CEE 7/3 sockets are pretty much the only thing I'm aware of for new wiring, with the unearthed CEE 7/1 sockets still present in older installations. Both are rated for 16A, with either 10A/1.5mm² or 16A/2.5mm² branch circuits from the distribution board. It would be unheard of to wire those up with any higher ampacity at risk of overloading the sockets - although recent experience with e.g. EVs has shown that they're not actually suitable for sustained loads at 16A, given e.g. wear and tear on the sockets.

Unearthed appliances do commonly have CEE 7/16 plugs rated for 2.5A, particularly things like wall warts or USB chargers, which does fit into a CEE 7/3 socket.

I recall seeing CEE 7/16 (2.5A europlug) sockets, although those may have been imports from elsewhere in the EU. I suppose those would have the same issues if wired up to the same distribution circuits. But extension cables for those are rarer, the only ones I've ever seen are CEE 7/7 plug (16A) -> CEE 7/16 sockets (2.5A).

For residential/commercial loads over 16A / 3.2kW, it's all CEE / IEC 60309 connectors, and those are treated like distribution circuits with overload protection sized appropriately for the connectors/cables.

Is "ampacity" really a better word than "current"? And the unit symbol is just "A", like "30 A".

I realize I'm nitty but this is a technical-minded forum after all.

"ampacity" means "capacity in amperes" or more literally "ampere capacity." You could say current capacity too but it takes longer. Ampacity is the language used in the electrical code.

"amp" also seems to be more common to write than "A" for electricians. Remember that the SI standardization of unit abbreviations is actually a pretty modern thing, so lots of fields existed before unit abbreviations were standardized and continue to use existing practices.

Ah I did not get that meaning, then obviously it's a perfectly cromulent word. Thanks and TIL.

Nah, it's fine to be nitty. If you glance at my comment again, you'll see my usage devolve from A to amp halfway through, my brain can't help but write what it sounds like to me.

Yes though, ampacity is the correct word (for my home country). "Current" is an instantaneous measurement of current flow. That they use the same unit is pretty convenient for planning circuits. https://en.wikipedia.org/wiki/Ampacity#:~:text=Ampacity%20is....