I am kind of confused about the Live and Neutral wires in Mains wiring. I've seen YouTube videos where someone touches the Neutral wire, but it doesn't shock them, but touching the Live wire does.
Aw, what the heck, I'll wade in here too....
1) From Kirchhoff's current law, we know that the current
into a mode must equal the current
out of that node. If you have a load (light bulb, motor, heating element, whatever) between the "live" (black) and "neutral" (white) AC wires,
both wires are carrying the same current. Yes, it's reversing 60 times per second (in the USA), but the current has to be the same. And if the current is reversing... which side is the "source"? The electron flow isn't "stronger" when the black wire happens to be positive, or vice versa. That white "neutral" wire is carrying current and can shock you. Does this change if it's connected to a copper grounding rod? Does the distance from said copper grounding rod matter? What is the inductance between the node in question and the copper rod connection? Are you CERTAIN there are no wiring errors in your house? We can argue about the finer details but are you willing to bet your life on it?
2) To understand where the concept of "neutral" originates, think of a center tapped transformer with its 240VAC output connected to your breaker panel's input. If you connect a 240VAC load (like an electric furnace, electric oven, electric dryer, etc.) then the reversing electron flow occurs between the two "live" wires (black and red) and the center tap (white) would see no current flow. Indeed, many such appliances don't even require a connection to the center tap (white) for precisely this reason. But what happens when you connect a 120VAC appliance? Now the circuit is closed by the center tap (white)... and that center tap is conducting current, as explained in #1 above.
3) All of the above is based on relative voltage potentials. For current to flow, there must be a voltage differential - and a voltage is always measured relative to some reference point. From one point of reference, the center tap (white wire) sits at zero VAC because it's the center tap of the power company's transformer and the 240VAC legs (black and red) oscillate around it. However, if you connect an AC voltmeter from black to white, or red to white, you'll still measure AC voltage. Go ahead, reverse the leads of the voltmeter - the AC voltage is still there! {grin} And if YOU are a current path between any two nodes of differing voltage, you can conduct current. The electrons don't care that you're a human. They don't care that there's another, perhaps lower reactance path in parallel with you. Some of those electrons will be happy to use you as their path to complete the circuit, and your body won't be happy that they do. We must respect electricity because electricity has zero respect for us.
I've seen YouTube videos where someone touches the Neutral wire, but it doesn't shock them, but touching the Live wire does.
YouTube is the modern-day equivalent of Darwin, always trying to clean up the gene pool!
Under certain circumstances, if you were fully and completely electrically isolated from everything else, you could touch even the black or red wire - by itself - and not get shocked. Technically your body would be raised to the same AC voltage potential but since you'd only be in contact with ONE point, there'd be no opportunity for current to flow. This is why birds can sit on power lines, Tesla has those photos of himself being raised to hundreds of kilovolts, etc. It's not solely about being at any given voltage potential... it's about current flow. Current is what kills you, voltage just makes the current possible.
Bottom line: It is NOT inherently safe to cavalierly touch the center tap. When I'm working on AC power, I presume ALL wires are potentially lethal. I kill the breaker in question and then I ALSO check using a handheld "power checker" (electric field detector) that I've tested on a known-live circuit moments before. And even then, I don't touch more than one wire at a time if I can help it. This is your life you're gambling with.