The American NEC mandates them where they're necessary, just as in the UK.

Provided the current doesn't leak to earth, then its perfectly possible for an ELCB to continue to happily feed current up one arm and down the other, an ELCB will not trip under those circumstances. They measure current imbalance between the L and N, if the difference exceeds some nominal amount, often 10..20mA, the circuit opens. The expectation is that the imbalance is flowing to earth via you.

The IEE regs only seems to mandate ELCBs on certain circuit types, and the same ones as the US regs have mandated ELCBs

Please don't extend your lack of electrical knowledge to a practical demonstration. What you propose may well kill you.

There are many layers of transmission voltages, down to about 6.6kV as it goes down the street to a substation in the UK, down, IIRC, to 3.3kV in the USA
It depends on the lengths of the lines, and the loadings. The USA uses quite a lot DC interconnections these days, as we do with the Channel interconnector and the new Scandanavian connectors. The multiples and ratios are well controlled and international - and the USA uses them too.

There was the amusing day an electrician connected one phase positive to negative in a power dist room, and caused [500 machines?] to start smoking regardless of on or off or switched off at the wall socket - but then he was operating years before elcb's when i think about it. Same guy later seen drilling into switch boxes to affix 'dangerous 415 volt' labels - i considered giving him double sided tape but we decided the possibility of a darwin award for him was overwhelmingly a superior choice...

There is no "positive" and "negative" in an AC system. He MIGHT have connected a Phase to the Live terminal and a Phase to the Neutral terminal though. That would put 415V out.

In your language, he connected a 50 amp live or positive wire to a neutral or negative terminal post, causing instant bad karma to anything plugged into the phase regardless of switch state.

Any given phase swings positive and negative wrt neutral and ground, so which is it ?

Steve is speaking "electrical". As he already told you, there is no "positive" or "negative" wire in an AC system.

So my electrical knowledge and gadget/tech knowledge are both about zero.
As long as my electrical item or its charger says 90-240v or similar I can use it in the US with an adapter? From a quick hunt around the house I can see that my Sonos and my laptop charger both have the right credentials but my nutribullet does not. So kitchen equipment has to go but the rest is ok with an adaptor. Is that about right??

That is a pretty good summary. You should be able to buy a suitable power cord to go into your laptop brick once you get here saving the hassle of a wobbly adaptor as US sockets do not seem to hold the plug very securely.

About, your nutribullet is probably quite powerful - so not suitable/cheap enough for them to make a variable input supply, cheaper for then to just make it with different motors or different wiring [do not attempt to change it...]

Commonly called an iec or kettle flex, but make sure it fits, there are variable designs...

Types - https://www.broadbandbuyer.com/featu...d-identifiers/

As well as getting the correct end for your brick (kettle style, figure of 8 or cloverleaf) you will need to get the correct US end too - a 2 pin will fit in a 3 pin (grounded) socket, but a 3 pin won't fit in a 2 pin (ungrounded) socket. Our house has mostly ungrounded sockets (outlets) but one grounded per bedroom, usually the one operated by the light switch.

Yeah, british plugs with adapters do not play well with US sockets. And you can probably pick up a new cable for less than the price of a plug adapter.

Both ends of the cable have specific names. For reference, "kettle style" is C13, figure 8 is C7, and cloverleaf is C5. For the wall socket, you want NEMA 1-15 (2 pin unearthed) or 5-15 (3 pin with earth connection).

Oh yeah, americans arent allowed to make their own sometimes are they? Ie can you buy a plug by itself and just cut the flex, strip the conductors, fit the flex and screw it together as we would do in the uk?

We also have adapter plugs in the uk when we import stuff, a us or euro plug inside, clipped into a uk plug. Maximum luck would be to find you had one of these.