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What is US standard ac voltage supposed to be?
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Just be aware that, depending on your installation, you may get as low as 105V. This seems to be common in older buildings (60s and before) where fewer circuits are used and you turn on a large load. In many places building code doesn't require retrofitting.
If the question is related to computer power, rest assured, switching power supply will take anything between 100 and 240V.
If the question is related to computer power, rest assured, switching power supply will take anything between 100 and 240V.
I spent my college summers working as an electrician 4 decades ago and distinctly remember 115v or was it 110v? 
I noticed the comment that voltages varied based on time and place in the States.
I noticed the comment that voltages varied based on time and place in the States.
So, it's 120VAC, but might be something else. I've always referred to line voltage as 110 or 220.
Power in Australia is commonly referred to as 240v a normal outlet is 240v/10amps although a normal power outlet can go anywhere as high as 240v/50amps, you just need to use better wire, bigger fuses and plugs and etc and of course a suitable power outlet that can handle it so you don't burn it out from getting too hot.
The difference between single phase and three phase is just the amount of wiring. Single phase electricity comes into your house with 2 wires (1 active and 1 neutral) 3-phase comes into your house with 4 wires (3 actives and 1 neutral).
There's nothing particularly special about it other than the fact that it can be wired up to suck more juice for items that require such as stoves, air conditioners, and heavy duty electrical equipment, welding gear, mechanical gear, etc..
Most electrical devices these days will happily switch over automatically at their transformers for anything between 110v and 240v you just need the correct socket adapter and your device will draw the power it needs automatically. The days of blowing things up by plugging them into power loads they can't handle are well and truly gone.
in Continental europe the voaltage was 220 and in the UK it was 240 ... using increedible hard math this was turned into the new 230v(+/- 10%) Standard
Fifty-some years ago, 110/220, 115/230, and 120/240 volt systems were pretty common in the U.S. The image below is from the November 1956 issue of Popular Mechanics, which suggested that 115/230 was perhaps the most common 3-wire system then in use.
When I was growing up, all the older electricians in town called it "110/220" because that was the voltages used by most of the area's mining companies that operated the power stations that supplied power to the "company owned" town in the Central Appalachian Coalfields, back when they were first installed in the early 1900s.
When I was growing up, all the older electricians in town called it "110/220" because that was the voltages used by most of the area's mining companies that operated the power stations that supplied power to the "company owned" town in the Central Appalachian Coalfields, back when they were first installed in the early 1900s.
The differences go well beyond the number of wires. Each "active" (or "hot") leg carries alternating current in a sinewave. In a single-phase service (not circuit, mind you, but service), there are two "hot" legs in opposing sinewaves. A circuit with one hot wire and one neutral wire is nominally 120 volts, whereas two hot wires (and no neutral) is nominally 240 volts, since the sinewaves are opposite each other.
In a three phase service, there are three hot legs, each a sinewave 120 degrees off from each other. In this instance, a single line voltage wire with a neutral still gives you 120 volts, two hot lines with no neutral gives you 208 volts (since the sinewaves are not opposite each other, adding them together does not double the voltage), and all three hot lines together in a circuit gives 208 V three phase.
In commercial services, these voltages may be increased to 277 and 480, respectively, depending on the service voltage.