In US residential wiring, you can use live wire detectors to detect live wires at say an outlet. Only one of the outlet terminals is detected as live the other I assume is neutral. Since the home circuit is AC, there is no positive and negative like DC. The voltage and current cycle polarity at 60Hz. So what makes a live wire different from the neutral wire at an outlet? Can you get an electric shock from a neutral wire? If not, why?
I read about split phase power supply but still clueless about questions above.
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In AC, one wire remains at 0 volts. The other alternates between +170 and -170 volts (in the US).
The one at 0 volts won’t shock you, but the one bouncing between +170 and -170 will do so easily.
The live wire has varying voltage in it, and a varying magnetic field. The neutral wire is grounded, a conftant voltage and thus no magnetic field.
AC has positive and negative, that’s actually why it’s called alternating. It goes to +120V (RMS) and -120V, alternating 60 times per second, in the US. The neutral is essentially 0V. In DC it doesn’t swing back and forth, you just have one constant voltage on one side and then 0V on the other side, so a 5VDC adapter will be providing +5 and 0 at its two terminals, giving you 5 volts.
The big difference as you can see is that one of the wires has a voltage potential and the other does not (0 volts). You are not likely to be shocked by the neutral unless something is really wrong, because the voltage potential is at 0 or close enough to 0 that it just doesn’t have the “juice” to really do anything to you.
You also asked about split phase, I believe you’re talking about 120/240. The transformer outside has 3 taps on it, one at either end of the coil and one in the middle. A connection between either end of the coil and the middle one gives you 120V, while a connection between both ends of the coil gives you 240.
The hot wire is the one actually connect to the input from the plant. You can touch the neutral and ground at the same time with no issues (assuming there isn’t a short somewhere or something wired incorrectly). Grabbing the hot and either one of those two wires is going to hurt.
The live wire, also called the hot wire, is the wire that has voltage always present. Typically 120v to ground. That means you have a voltage difference of 120V between that wire and ground, or just 120V. The neutral wire is the return wire. It doesnt have voltage on it. When a switch is closed which completes a circuit the voltage drops across the load and the current returns to earth by way of the neutral wire.
Split phase is where you get your 240V. However, this is not 240V to ground, it is 240V phase to phase. In this case you have 2 hot wires. Each wire is 120V to ground, but at one instance in time one will be +120V and the other hot wire will be -120V and it will cycle 60 times per second between being positive to negative and back. This is accomplished with a center tapped transformer which has its center tap grounded. You may need to read up on transformers to understand them more clearly.
Since the polarity cycles 60 times per second, the direction of current flow changes 120 times a second (2 polarity changes per cycles). That is why it is called alternating current.
Electronics require electronic diode bridges and capacitive/inductive filters to rectify a voltage source and smooth it out to provide a constant direct flow of current to sensitive circuits. This is how ac can be used to power computers.
I had it explained once like a water system. What comes from your faucet has pressure behind it. Hot wire. The drain line has no pressure but gives the water somewhere to go. Neutral wire. Instead of water pressure you have amps.
All wires should be considered “live” and treated with caution!
The main difference between the “hot” wires and the “neutral” wire is that the neutral is at ground potential. As has been stated in other answers, hot-to-hot is normally 240 volts RMS and hot-to-neutral is 120.
However, if the neutral wire is disconnected or severed between the load (outlet, light fixture, or whatever) and the point of grounding (iirc they are grounded at the breaker box as well as at the pole the transformer is on, assuming it’s an above-ground system), you will get 120 volts through your body if you touch the neutral and something grounded at the same time.
That’s why modern electrical wiring has a separately run ground wire in addition to the hot and neutral. It provides a means for equipment to be grounded without being part of the normal power-transferring circuit. This is especially important with things like power tools where the ground is bonded to the tool’s metal case.
Another strange situation I have witnessed is where the main neutral wire to the house is somehow disconnected from the source and is ‘floating.’ At that point, you only have two hot leads, one of which is wired to a bunch of outlets/lamps and another which connects to another bunch of outlets/lamps. And the common connection is the floating neutral.
So, when you turn something on that’s on just one side, nothing happens because the neutral is floating and can’t make a complete circuit back to the transformer. However, if you turn something on on the other side at the same time, you have 240 volts running through two separate devices between the hot leads via the floating neutral! (Yeah, sounds complicated ’cause it is.)
So you end up with weird stuff like some lights being brighter than others or some machines running faster than others, depending on the total resistance of the devices connected to either side. It’s truly bizarre. It can also, as one might imagine, damage equipment in one’s house.
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