AC current

[Clangy]

my question is Where does the current alternate on an ac circuit? does it happen at the power plant before its distributed or in the main power lines before a meter?I have an idea how it works just no idea where?:-? :-? :-?

 

[iwire]

my question is Where does the current alternate on an ac circuit? does it happen at the power plant before its distributed or in the main power lines before a meter?I have an idea how it works just no idea where?:-? :-? :-?

AC current is produced at the power plant.

 

[marissa2]

You might want to take a theory class it will explane it all to you, if the instructor is good.
Lou

 

[charlie b]

This is a long story, and I will give just a short version. Let me warn “those in the know” that I wish to hear nothing whatsoever on the topic of “drift current.” I know what it is, and indeed took a post-masters degree course on the topic. But I don’t want to confuse a new member of our profession, by getting too complicated too soon. Let us save that level of detail for another lesson, OK?

Current is “charge in motion.” In our business, the things that actually move, and that carry their own charge with them, are electrons. As they move in one direction through a wire, the charge they carry can be detected traveling through the wire in that direction. For “Direct Current” systems, the electrons are moving in one direction only. The amount of current, as measured in “amps,” is determined by the amount of charge that passes by a given point during a given time interval. That is essentially the same as saying current is measured by counting the number of electrons passing by a given point in a given time interval.

For “Alternating Current” systems, current will start off by having some small number of electrons moving in one direction along a wire. They start off at the source, travel to the load along the “hot wire,” travel through the load, travel back to the source via the “neutral wire,” and begin the cycle again. A few moments later, there are more electrons traveling in that circular path. A few moments later, there are still more. Some time later, there is a peak number of electrons moving in that circular path, and then the number keeps getting smaller. Eventually, the movement of electrons stops entirely.

Immediately thereafter, however, the electrons start moving again, but this time in the other direction. They start off at the source, but this time they travel to the load along the “neutral wire.” Then they travel through the load, travel back to the source, this time via the “hot wire,” and begin the cycle again. A few moments later, there are more electrons traveling in that circular path, a path that is opposite in direction to the initial path. The number of electrons moving in that path grows to a maximum, then becomes smaller, and eventually becomes zero. At that point, electrons start moving in the original direction once again.

The time it takes for this entire process to run, from zero current, to maximum current in one direction, to zero current, to maximum current in the other direction, to zero again, is one “cycle.” In the US, our AC systems have 60 such cycles each second. In Europe, they have 50 such cycles in each second.

 

[jcole]

great easy to understand, down to earth explanation charlie b. I might add to it that the power plants generator's armature cutting through the magnetic field created by the field windings at different angles is what creates this sine wave.

 

[Smart $]

my question is Where does the current alternate on an ac circuit? does it happen at the power plant before its distributed or in the main power lines before a meter?I have an idea how it works just no idea where?:-? :-? :-?

The truth of the matter is that current alternates direction through the entire circuit. The power plant(s) provides the alternating electromotive force through various stages of stepped up and then stepped down voltages. If the circuit is broken, e.g. switched off, the emf is still there but no current, thus no alternating current.

 

[LarryFine]

Charlie, the only critique that I would give to your explanation would be to simply say "the other circuit conductor" instead of "the neutral", but I certainly understand why you chose that terminology.

Bravo.

 

[Clangy]

Thanks guys

Thanks guys

That was very helpful. I appreciate it and will take theory to fully understand

 

[charlie b]

Charlie, the only critique that I would give to your explanation would be to simply say "the other circuit conductor" instead of "the neutral", but I certainly understand why you chose that terminology. Bravo.

Thanks, Larry. To be honest, I do not know what "common slang" terms are being taught to those just joining the profession. I think that "hot leg, cold leg" is probably on its way out (if not already locked outside). I also think that "ungrounded, grounded, and grounding" are too cruel to inflict too early on someone just getting started. So I picked a middle ground, and hoped it would be at least clear, even if imprecise or outdated.

 

[Clangy]

hot/neutral

hot/neutral

Your right. im not familiar with hot and cold leg, only switch leg. I do understand hot and neutral from work experience. grounded and ungrounded ive learned a lot about from this website. Thanks again. i never knew there was a load carried from the grounded (neutral )conductor during alternating invervals in the ac circuit, that is my understanding, hope im gettin it finally
Chris

 

[Smart $]

...the grounding (neutral )conductor...

Ummm... that would be the grounded conductor. A grounding conductor is also grounded, such as an equipment ground, but intended to carry no current except under a fault condition or during a lightning strike and/or imposed surge.

 

[Clangy]

i c

i c

The professor of my code class warned me about confusing them. Would this be an example of system grounding?

 

[LarryFine]

Your right. im not familiar with hot and cold leg, only switch leg.

The word "leg" simply means one section of a circuit, similar to one leg of a route, and the word "circuit" is also used to describe a closed loop such as a race track. Such a closed loop is required to have a circuit in both senses.

I do understand hot and neutral from work experience. grounded and ungrounded ive learned a lot about from this website.

When a circuit contains a neutral, it is the conductor to be grounded, if so required. Ungrounded refers to any other conductor, especially one 'hot' relative to earth, a grounded conductor, or (most often) both.

I never knew there was a load carried from the grounded (neutral) conductor during alternating invervals in the ac circuit . . .

In reality, the electron flow from the point of excess electrons (the 'negative' terminal) to the point of a lack of electrons (the 'positive' terminal) is not relevant to the flow of electricity from an ungrounded conductor to a grounded conductor, earth, or other grounded object or surface.

In other words, whether the moment in time is during the half-cycle where the 'hot' wire is positive relative to ground (or the neutral, the EGC, etc.), or the other half-cycle where the 'hot' wire is negative relative to ground, the hot wire will be the one considered to be the source of the electricity.

Alternating current merely means that the electron flow reverses twice per cycle, and yes, that means that 50% of the time, the source of electrons is the grounded conductor, but only in circuits with a grounded conductor. The alternating of polarity is the same regardless.

All AC circuits exhibit the same 'taking turns' of the conductors being the source of electrons, but again, the hot wire, the ungrounded conductor, will test hot relative to the earth. This would be true in DC circuits, also regardless of actual polarity.

In a car, for example, even in the days when many vehicles had positive-ground systems, the 'ungrounded', or 'hot' wire was seen as the source of electricity relative to the chassis and/or body. You could even have a car with neither battery terminal grounded.

Take a Corvette, for example, which has a fiberglass body. Every electrical component has a negative wire, because there is no all-encompassing metal cage to use as one giant 'neutral' conductor, or 'return path'.

In theory, either battery terminal could be tied to the metal chassis, and everything would work the same. You'd have two circuit conductors for every load, and one would simply be tied to the chassis. This is the basics of our grounded conductor.

The professor of my code class warned me about confusing them. Would this be an example of system grounding?

The grounding electrode conductor(s) and system(s) are system grounding. Bonding a circuit conductor to the grounding system is, in some cases, optional, but grounding/bonding non-current-carrying conductive parts is practically universal.

 

[mattsilkwood]

an easy way to think of it the GROUNDED conductor finishes the circuit,i.e. on a light you have an un grounded (hot) and a grounded (neutral). the GROUNDING is there in case of a fault, which will be bare copper in residential or green in commercial

 

[mattsilkwood]

i tried to draw it but can figure out how on here but think of a waterbed, when one part is pushed down then the other part is up, that is the sine wave to be VERY simplistic.now on a single phase you have two waterbeds while one is up at its highest point the other is at its lowest.
google ociliscope and it should give you a little better description than what i can.

welcome to the forum

 

[Clangy]

single phase ac generator

single phase ac generator

great easy to understand, down to earth explanation charlie b. I might add to it that the power plants generator's armature cutting through the magnetic field created by the field windings at different angles is what creates this sine wave.

I just saw a video on how this works. I understood it well thanks to your explanations. although the current alternates, it is still convential current flow, thats interesting