Why are wall outlets 110V or 220V? Those seem like such arbitrary values; why not 100V?


Why are wall outlets 110V or 220V? Those seem like such arbitrary values; why not 100V?

In: Technology

It was tough in the early days of electricity to figure out what was the best voltage. Edison liked DC, it worked well but required heavy wires and could only be sent short distances from the generating station.
Westinghouse and Tesla liked AC which didn’t require heavy wiring, but was more dangerous to work with and required heavy transformers, but it could be sent long distances with ease.

So many different schemes were tried, and they settled on 110v as a good balance between wire thickness and distance and dangerousness.

Plus it probably just fit well with the generators they had built. That’s why a lot of things end up like that. Some guy built something and arbitrarily picked a figure because it made it easier to build and therefore cheaper than all the competitors.

you may be surprised to find out that the power coming out of your outlets isn’t actually 110/220/whatever the standard is in your area.

don’t recommend this to people without some background in working with electricity, but you can check an outlet with a multimeter designed for the job – has to be one designed to handle wall socket currents, cheap shit will explode in your hands, don’t do it.

I can see anything from 100V to 116V in Toronto in the same house on the same day.

Tokyo had clean power, never budged from 100v.

This might not be a simple ELI5, but the history is based off of common 1.5V battery cells and 6V DC power supplies before AC was widely implemented. Any combination of power could then be made with multiples of 6V (6V, 12V, 48V, etc) and they were sometimes rounded for simplicity. Thus 6V x 40 DC batteries = 240V.

But through the AC and DC “War of Currents” between Edison and Tesla, Tesla won with an implementation of AC and originally planned 240V but decided 120V (half of 240) was safer in the household and more efficient at 60Hz. 240V was originally chosen technically because of phases and less line loss during transmission, but probably more detail than needed for ELI5.

120V was also thought to be enough to power most household appliances and probably more importantly the original filament light bulb was designed to be used between 100V and 130V. This alone might be the easiest ELI5 reason – everyone in that day and age wanted lights like today’s cellphone.

Additionally, all US homes are still fed with 240V at the main panel (2 hot legs) but most outlets except for dryers, ovens, etc only get one hot leg and therefore 120V power.

The US then standardized on 120V and AC beat out DC.

Most of the rest of the world just choose 240V, which is arguably more efficient and accomplishes the same thing. In cases like when England rebuilt after WW2 it was that 240V was more efficient for trqnsmission and therefore required less copper wiring so economics played a big part of that decision.

You can find out more technical detail, but this is probably enough for ELI5.