What keeps the Electric from shorting to ground? On my electric panel the Neutral is tied to the ground. The ground is a bare copper wire run back to my water main. a. Electricity chooses the path of least resistance. Is the current happier to go back to the power supply rather then ground which is right there in the house basement?
Why does the AC that comes into the house have 2 wires for the Hot leg and 1 un-shielded wire for the Neutral Leg? If it’s tired to ground I guess it doesn’t need to be shielded. But it will still have the same amount of current flow on it as the Hot leg. The Neutral wire is live wire...
Is neutral supposed to be wired/bonded to ground ?
Current wants to return to source, not to earth
Yeah, OK. Lightning's source is actually earth. The same be said for ESD, aka "shock on the doorknob" static electricity.
However, for human-made electricity, that wants to get back to the artificial source - typically the supply transformer.
Transformers are insulated, so the two sides are not electrically connected. The secondary winding's electrons do not want to get back to the primary. Unless it's leaking (failing insulation).
The neutral-ground bond
Your instinct is not wrong. You are thinking of an isolated system where none of the conductors contact earth. I have had three such systems; two are intended and one was a malfunction, a loss of that same neutral-ground bond that worries you.
For instance, the three wires would be hot1-120V-neutral-120V-hot2 relative to each other, but nothing (isolated) compared to earth. If you grab earth and hot, nothing happens. Great idea, right?
The problem with isolated systems is they don't stay isolated without active labor of site maintenance electricians, e.g. In a factory. You end up with leakage from something to one of the wires or transformer windings. In my malfunction, I had a leak from Earth to Hot1. So now,
- Earth to hot1 is 0 volts
- Earth to neutral is 120V
- Earth to hot2 is 240V
So now, touching hot1 is safe, but hot2 is twice as bitey. In 230V Europe, "twice as bitey" would actually mean 400V because of their 3-phase. That's nasty business!
Even worse, what if the leak is in the 2400V transformer?
- Earth to hot1 is 2400 volts
- Earth to neutral is 2520V
- Earth to hot2 is 2640V
So you see, if you leave Fate to choose the first leak, you get Fate's choice instead of your own. But if you force the choice, you can "peg" it where you want. Then, the first leak becomes the second leak, completes the circuit, and allows circuit breakers to protect you. In my malfunction, as soon as I installed the neutral-ground bond, that other hot-ground bond leaked enough current to hard-trip the breaker.
And because neutral is bonded to ground, the hots cannot be more than 120V from ground. That's the whole idea.
For the neutral-ground bond, we use a strap of copper because it's cheap. But imagine what would happen if we used a 1-volt transformer?
- Earth to hot1 is 121 volts
- Earth to neutral is 1 volt
- Earth to hot2 is 119 volts
Any problem with that? Nope, this would serve all the purposes of a neutral-ground bond, and would be very useful for troubleshooting.
Once we pick the conductor that is bonded to ground, we name it "neutral". The code books call it the chalkboard-scratching term "grounded conductor", i.e. The active (normal current flow) conductor which is grounded somewhere (but not here). We plan for it to be near ground, but if a neutral wire breaks, neutral may ride up near hot voltage. That is why we insulate it like a hot.
Your panel has all the neutrals and grounds all mixed on one bar. That's kind of "all your bars being the neutral-ground bond", which is legal, but tacky and misleading. Best practice calls for rigid separation of these two, neutrals on the neutral bar, grounds on the ground bar (which you may need to buy as an accessory), and one specific neutral-ground bond and bonus points if you can easily remove it or get a clamp ammeter around it.
Ground is an interesting thing. It protects in a number of different ways, some of which make use of it being (essentially) the same as neutral, and some of which are based on the connection to the earth (e.g., copper water pipe). The end result is:
Ground and neutral are tied together in the main panel, and only in the main panel. Because of that, it is legal (debatable as to whether it is good practice or not) to have ground wires & neutral wires going to the same place in the main panel, rather than "all grounds to a ground bar" and "all neutrals to a neutral bar" and one connection between the ground bar and neutral bar.
Ground must be connected to copper pipes that go into the ground and/or connected to a metal rod driven into the ground or buried in concrete. The specifics get complicated. But it is important to know because if you replace your copper plumbing with plastic, all of a sudden your ground isn't going to work properly (i.e., safely).
Electricity does choose the path of least resistance. So almost all the time that means electricity does NOT actually go to your water pipes but rather returns via the neutral. Earth (especially wet earth) conducts electricity, but not nearly as well as copper or aluminum wire. But there are certain situations (e.g., lightning strikes) where current really will flow to that copper pipe into the earth.
Not only copper pipe but any metal pipe and even ductwork is supposed to be connected to the grounding electrode system. Gas pipe, too, but gas pipe is not part of the grounding electrode system. Electricity wants to return to its source and earth is not a good conductor so the neutral is the easy path back.
Yes in the main panel they are supposed to be connected. The reason for the 2 hots and neutral is your power is coming from a 240v centertapped transformer. The voltage hot to hot is 240 and the hot to ground is 120v L1 is 180 degrees out of phase with L2. This is why the neutral can handle the 2 hots. The grounding system is there to clear a fault without having become energized. In years past the neutral was used as the grounding method but when things go wrong this energizes the frame and created an unsafe condition.
Since you only mentioned a water pipe this should have a minimum of 10' of earth contact. I would suggest adding a supplemental ground rod to your system. A few years back the utility replaced all the metal pipe in an area and this eliminated the ground for many homes, the home owners were not informed that this could cause problems if there only ground was a water pipe that almost every home had in that area. Listed ground rods are usually under 20$ a clamp and some number 6 copper wire back to the panel is a good idea.
Electric current is only useful to us if it can eventually get back to the ground, after it has passed through a light bulb or motor, for example. Electricity is a potential force and wants nothing more than to get back to the ground. We let electricity get to the ground but only after it has passed through some appliance or other load. As a comparison, the water coming out of your kitchen sink faucet is only useful if it can eventually drain, but of course only after it passes over your hands or dirty dishes.
Some of the other answers seem overly complicated to me, so...
Both neutral and ground are at, or should be at, Zero Volts.
Neutral wires carry current. That's the difference.
At your panel, there are two hot wires, out of phase, of 120 volts each, so it's 240 volt AC coming into your house. The higher the voltage, the further power can be transmitted without power loss.
That's because you're on TN-C-S system where you have a single common PEN wire hooking your home to the transformer that is 'splitted' at main panel in protective earth (PE) and neutral (N). It's done because an RCD breaker (aka GFCI) can find a leakage current between the neutral and earth and open the circuit before you get fried.