Split-phase power is only common in the US and other countries with 120 volt (+/- 5%) mains. In the 230 volt (+/- 10%) world, it is typical to power single-phase loads either across two phases (delta) or between a phase and ground (wye).

While the second half of your comment is correct:

>> The electrical outlets in your home have two power-carrying prongs.

>Only one of the prongs carries power. The other is attached to the earth, and is always at zero volts.

Voltages are about potential differentials, so "zero volts" is relatively meaningless without context.

The neutral line is required by the electric code to be connected to earth at the electric panel, but even if it were not, any ungrounded appliances would work correctly.

Both prongs absolutely carry power. Slap an ammeter on the neutral line; it should be identical to that on the hot line. Don't actually do this, but if you were to cut the neutral line with a live circuit, you would see sparks. This is particularly important when working on circuits with a shared neutral (two hot lines on alternate halves of the split phase with a single neutral line); despite the breaker being off for your hot line, you can get shocked when working on junction boxes for the neutral line. Yes this is up-to-code in all states (though a few places either recommend or require ganging the circuit breaker when doing so).

>> and then they will slowly switch places over the next 1/120 of a second so the right wire is at +170 volt

> No. The power prong (the smaller one) will switch from -170 to +170. The other one (the neutral) is always at zero (measured relative to you).

Here you use voltages as a relative measure, which is correct. As a nitpick you do assume that the person is grounded. Walking on carpet in the winter, I can be at a potential of thousands of volts away from that though.

[everything from here after in ars's comment is correct and I have no more nitpicks]

> Both prongs absolutely carry power.

Both carry current. But not power. Power is volts * amps, and the neutral is defined as zero volts (if you ignore the voltage drop).

> you can get shocked when working on junction boxes for the neutral line

Only from the voltage drop on that wire. It's not the full 120v. (Unless it's cut of course, but that's a whole different story.)

> Here you use voltages as a relative measure, which is correct.

First you introduce the concept, then later, explain other less important details. And that's how I wrote it.

> Walking on carpet in the winter, I can be at a potential of thousands of volts away from that though.

It's a good nitpick :)

If you are going to take the view that the neutral does not carry power, then the phase wire does not either. Ignoring volt drop, both wires have a 0V difference between each end and so no power is dissipated in them. Power is only dissipated in the appliance (except in reality, where volt drop is responsible for significant losses between generator and consumer)

> both wires have a 0V difference between each end

Obviously voltage is relative. So I'm measuring with respect to me. With respect to me the hot has power, and the neutral doesn't.

i.e. If I attach a light bulb between me and either of the two electrical wires, will it light?

But you're right "carrying power" is a poorly defined term. The problem is that it's hard to use a term that is both clear, and strictly correct.

>Both carry current. But not power. Power is volts * amps, and the neutral is defined as zero volts (if you ignore the voltage drop).

What he has already pointed out is that voltage is a relative unit. Zero volts by itself is meaningless. It would be just as correct to say that the hot wire is at zero volts and the neutral wire and the rest of the planet are at 120VAC. Also earlier you mentioned that from phase to phase inside a house was 240v but phase to ground was 208v. This isn't correct and it's simple trigonometry to prove why. You can visualize voltage potential in any polyphase AC system as the distance between points on a circle. Ground is the center of the circle and the individual phase is a point on the circle offset by the phase angle. For a split phase system there is 180 degrees between the two phases and cos(0) - cos(180) gives you the fairly obvious distance of 2x the radius. This means for 120v from phase to ground you get 240v phase to phase. In a three phase system there's 120 degrees between phases so if you have 120v from phase to ground you have (cos(0)-cos(120))*120v=208v. For what you're saying to be possible you would need 98.85 degrees between phases which is obviously not a nice integer division of 360 degrees.

High voltage transmission lines can carry power without a neutral wire because they use the earth as a neutral, but in your house you can be damn sure the neutral is carrying power. Cut off the neutral blade on your appliance if you want to check it out.

"Electric power in watts produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an electric potential (voltage) difference of V is

P = work done per unit time = VQ/t = VI

Note that V is the "electric potential difference" and it take two conductors to supply power.

I think it's incorrect to say that a single wire "transmits" power. Both a current and a voltage difference need to be transmitted to transmit power. So it's really the distribution system as a whole (in this case, neutral and hot together) which transmit power.