Title, really. I recently had to reverse the polarity of a badly installed receptacle. I read that the current will work either way but I could shock myself on the light bulb socket, for instance, if the receptacle has its hot and neutral reversed. But why any of this matters when the current is constantly changing direction anyway? Why is the neutral “safe” ?
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Simple: There isn’t much difference between “neutral” and ground. Your neutral line is connected to ground at the point where it comes into your house. So if current can go from your to neutral, it’ll go from hot to ground about as easily.
So, touching the neutral wire while also touching, say, a metal faucet handle will not shock you (except in really unusual circumstances where something else has already gone very wrong). But touching the hot wire while touching that metal faucet handle WILL shock you.
This is handy for a few reasons. One reason is that you can use hot+neutral for 120V for most things, but power appliances that need more power with hot+hot (using two of the three phases) to get 240V.
It also simplifies the design of some small appliances: because you have a “hot” and a “not hot” wire, you can switch it on and off by disconnecting the “hot” wire where it enters the appliance. There’s no need to disconnect the neutral wire also. If you used “hot/hot” then your switch would be to disconnect both wires.
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