Mivey, you sure put up a lot of words there but you're missing (while confirming...?) my point.
Well George, whether or not you learn anything is your responsibility, not mine. I am willing to help others learn but I can't drag someone kicking and screaming to a better understanding because knowledge requires effort from those who would aquire such knowledge. You can lead a horse to water but you cannot make it drink.
I have three lamps, all connected phase to neutral. All lamps draw 10A of current. They are supplied from circuits 1, 3, and 5. As I turn them on in sequence, why does the current disappear from the common neutral when the third breaker is closed?
Because the path back to the first phase has a lower energy solution THROUGH the other phases because the loads and phases work together. The other phases ARE NOT the destination but provide a shortcut, so to speak, back to the first phase.
If the preferred destination were not the phases, wouldn't it show 10A on all four conductors - all phases and neutrals - using the neutral on different wavelengths averaging 10A overall?
If you had 10A of incandescent on the first phase, 10A of motors on the second phase, and 10A of computers (or maybe a capacitive load if you could think of one) on the third phase then you will have neutral current because the phases don't all work together and some of the current will find a lower energy path through the neutral BACK TO IT'S ORIGINATING PHASE. The neutral current may even be on the order of 6-7 amps or more for a quick calc I just made.
Whatever route the current takes, when it reaches the common neutral point at the transformer, it goes back to the originating phase, NOT some other phase like your analogy proposes.
Also think what happens if you have 10A, 1A and 1A of similar type loads. The other phases only share their path to the extent that their loads are complementary. If the phases are the preferred destination then they would share their half of the 10A load but that is not the case as most of the 10A takes the neutral path. In fact they only share about 1A and the neutral takes about 9A.
Why can I open the neutral with even loads on all circuits and the lights stay evenly supplied?
Because IF the load on the other phases is complementary to the first phase, they can "carpool" so to speak and work together in a lower energy state. In other words, the current path back to the first phases has an easier route THROUGH the other phases, but the other phases are not the destination.
If the load on the other phases is NOT complementary, then the easier route back to the first phase is through the neutral. Note the destination for the first phase current is still the first phase.
If the load on the other phases is partially complementary, the some of the first phase's current will take a path through the other phases and some will go through the neutral. The destination is still the first phase.
In no case will current from the first phase that reaches the N point on the transformer seek to go through the windings to the other phases as your analogy states. That is where your analogy is wrong and where you are teaching your students incorrectly. It is up to you whether or not you can accept that bit of knowledge.
Your novel about dump trucks and pickups and so on did not clarify your ire about my simple analogy.
It may have seemed like a novel but I was only trying to help you understand.
I have not claimed it was perfect, but I did not think it was on par with "electricity seeks earth." In fact, I take exception to that because my lead in to using this animation in class is to firmly refute the earth's role in normal current flow.
I find it interesting that you would use an incorrect analogy about current destination to refute another incorrect idea about current destination and not see the correlation.
I also find it interesting that you use the same analogy in teaching a class that you have used here. Have you considered that you might have taken a defensive posture against changing your analogy?
The source the current seeks is not the other phases but its own originating phase. The current may or may not use a path through the other phases but the other phases are not the destination.
I'd hate to sow a bad seed, but you're not making your case well enough to inspire me to edit it.
I'm not sure I'm trying to make a case, just trying to pass along knowledge. If you want to continue thinking the destination for one phase's current is the other phases then no amount of information will change your thinking until you decide you want to know if that is actually true or not. For you to learn, you have to meet me part way or there is no exchange of knowledge.
I certainly appreciate the interaction on these topics, your replies, and the time to think on these things. But if it comes to where there is no exchange of knowledge, that would hold no interest for me at the moment.
