Alternating Current: neutral & ground

[ryancousins]

I'm having a difficult time understanding precisely how alternating current works in relationship to ground (earth). I have spent hours trying to learn online and I get conflicting explanations.

So let's start with a power plant. A coil of wire is rotated in between magnets, inducing a voltage. Does the generator have to be connected to ground for there to be a potential difference, or is their a difference and hence a voltage independent of earth?

Either way, the hot wires enter a home and power various loads. The neutral wire leaves these loads, and the voltage potential to ground is ideally zero or near zero. Would this not happen if the neutral and ground were not bonded at the main panel of a house? If alternating current switches direction back and forth, but neutral has a zero voltage, then how can it do work when the current is traveling from neutral to hot?

In other words, besides our optional but wise use of ground for fault safety, is it required as a zero reference, or would there still be a voltage potential between hot and neutral in our electrical system never contacted ground?

 

[meBigGuy]

See if this helps
https://www.physicsforums.com/showthread.php?t=705961

Takes a while to get to the meat, but it's worth it.

Ask any further questions, of course.

 

[meBigGuy]

BTW, I summarized it for a 60 amp 240VAV main with neutral as (neglecting power factor):

Again I learn something I thought I knew (thanks for that). The 60 amp service can supply 60 amps on either or both legs. The neutral conducts up to 60 amps as required by mismatched loads. If the loads are matched it conducts zero (since the matched loads are a perfect voltage divider and the middle point is 0V). Cool.

 

[jim hardy]

Most folks start out confused about "ground", probably because of early imprinting.
We see lightning bolts go to the ground, and we see our Dad make sparks when the lamp he's fixing shorts out, so we come to believe electricity has some curious affinity for the ground.

In other words, besides our optional but wise use of ground for fault safety, is it required as a zero reference, or would there still be a voltage potential between hot and neutral in our electrical system never contacted ground?

The question is asked here often.
And you already know the answer:
Does a flashlight work okay with no connection to earth?
Does the DC power system in your automobile work okay? It is insulated from earth(ground) by the tires.
Does the AC power system in an airplane or the space station work okay with no connection to earth?


A 120 volt household generator from Home Depot would work just fine on the moon were there any air to run the engine ...


"Earth ground" is just another wire that happens to go most everywhere.

Remember - voltage is potential difference, not just potential.

Here's another thread or two on the subject:

https://www.physicsforums.com/showthread.php?t=526008

https://www.physicsforums.com/showthread.php?t=506179&

 

[alphy]

I understand your confusion and conflicting explanations about alternating current and its relationship to ground. Let me try to provide some clarification.

First, let's discuss the power plant and the generator. The generator does not necessarily have to be connected to ground for there to be a potential difference. The induced voltage in the coil of wire is a result of the rotating magnetic field and the movement of the wires, not necessarily the connection to ground.

Now, when the alternating current enters a home, the neutral wire is connected to the ground at the main panel. This is important for safety reasons, as it provides a path for excess current to flow in the case of a fault. Without this connection, there could be a buildup of excess voltage and the potential for electrical shock.

However, even without this ground connection, there would still be a voltage potential between the hot and neutral wires. This is because the alternating current is constantly switching direction, creating a back-and-forth flow of electrons. This flow of electrons, or current, is what powers the various loads in a home.

To answer your question about how the current can do work when it is traveling from neutral to hot, it is important to understand that the neutral wire is not at a constant zero voltage. The voltage on the neutral wire is constantly changing in relation to the hot wire, depending on the direction of the current flow. This allows the alternating current to do work in both directions, from neutral to hot and from hot to neutral.

In conclusion, while the ground connection is important for safety reasons, it is not required as a zero reference for the alternating current to do work. The voltage potential between the hot and neutral wires would still exist even without the ground connection. I hope this helps to clarify your understanding of alternating current and its relationship to ground.