Do Common Ground Electrical Sources 'Swap' Holes and Electrons - Page 1
Forum section: electronics / beginners

author: jjcrawford1990
author_rank: Newbie
timestamp: July 30, 2022, 08:03:48 pm
content: So I see myself as a person who has to understand things at a very fundamental level to really retain information.And studying my electrical engineering degree, I find myself going to some very fundamental questions that I always had niggling me but never really had explained, presumably as it didn't need explaining.However, if we had 2 DC sources with a common ground connection. The flow of Electrons (shown as 'E') I've always assumed as being a push-pull from the power source. However, if the ground is combined, how are these electrons/holes unique to that source, or in reality, do the electrons and holes' swap around and thus as long as the flow of electrons matches the charge, the original 'source' of this electron push-pull is inconsequential.Sorry if this is inane rambling but I cant find a suitable question on google to satisfy me!Thanks for your help!Josh

author: golden_labels
author_rank: Super Contributor
timestamp: July 30, 2022, 11:25:38 pm
content: That is not insane rambling and there is nothing wrong with you. The confusion seems be arising from mixing two separate models.One islumped element model, which is not having electrons, holes or any other charge carrier. It’s only pure numbers that describe energy potentials and flow, without actually being concerned with the underlying mechanism. The model is not limited to electric circuits: for example it is used to describe heat transfer too.The other is describing the behaviour of individual charge carriers or groups of such at low level in particular materials, when considered in a particular electromagnetic field. That one resides on the intersection ofmaterials science, electromagneticism and quantum physics. Due to the sheer amount of particles involved and complexity of modelling the EM field, it’s absolutely unsuitable for describing even the simplest electronic circuits.Mixing of different charge carriers will not happen magically just because you connected e.g. a BJT transistor and a chemical battery in a manner shown in your picture. To start with: the wires are likely metal conductors, so your circuit is already limited to having electrons as the carriers at the large scale. Which means there is normally need to concern yourself with the second model in such a scenario. Any mixing would happen at a different level and in the lumped element model would already be represented as a single number or function. If you are concerned with particular charge carriers, it’s deep within a tiny piece of some substance. That’s the subject for the second model. At this point the lumped element model will either collapse completely or be useful only to convey the very general idea of operation (e.g.thyristor explanationon Wikipedia) without offering predictive power.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 20, 2022, 05:36:37 pm
content: The carriers are static (more or less) inside the crystal lattice. Cha

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: August 21, 2022, 04:18:22 am
content: Also, notice that there is no closed loop that includes the two sources. Therefore there is zero current in the ground connection between them (the part you have circled). One can be supplying 12 uA and the other 1200 A and this will still be true. All currents flow in loops. Any current supplied by the top of any such source must find its way back to the bottom of the same source.

author: MrAl
author_rank: Super Contributor
timestamp: August 22, 2022, 08:00:20 am
content: Quote from: jjcrawford1990 on July 30, 2022, 08:03:48 pmHi,The first reply here outlines the reasoning behind which this question is based. The theories used in a given situation have to match the physical level of the questions being asked. In most electrical circuit we can think of the components as idealized and complete in their own right. It depends how we view them though as to what kind of theory we are going to use, and sometimes an electrical problem using circuit theory turns into more of a true physics problem using physics theories that delve deeper into the origins of the electrical problem.Another example is conventional vs non conventional current flow. In order to understand that we cant use circuit theory alone we have to go into the physical laws that govern current flow itself, even if we just stick to classical theories, but we cant figure this out using resistors and voltage sources because the answer is much deeper than that; more fundamental.We cant answer a question like this using resistors and voltage sources but going just a tiny bit deeper into classical theory for this particular circuit, i would say there is no interaction because all the fields involved are conservative. That i believe is because both sources are DC and DC sources dont transfer energy in any way other than a direct connection. Now if one or both sources were AC sources, then we would have to consider a lot more like the physical orientation, physical symmetry, and the like, because AC sources have constantly changing fields which means there is always some interaction and some exchange of energy except maybe in the perfectly symmetrical case, but even then there could be oscillation where energy is passed back and forth even though there is no net change. Maxwell's fourth equation deals with changing fields, so what we are really looking at here is do we have something that acts like an antenna or coil of wire and is the current changing. If the current is a constant 1 amp then there will be no radiation, but if the current changes from 1 amp to 2 amps even slowly (which represents an acceleration of sorts no matter how mild) there will be at least some radiation and thus interaction between the left and right halves of the circuit at hand. DC circuits however do not interact when connected by a single metal wire.It still might be interesting to look into the wire and think about what is actually happening. The way i understand it is that the electrons do not move in any kind of laminar type motion, they move more like a as a turbulent flow. That means that they are constantly changing direction and thus some constant acceleration (however small) and that in turn means that there might be something measurable outside of the wire besides any static fields. This would most likely be a random change in the fields which averages to zero even at a somewhat close distance to the wire. This view would suggest that there could be some interaction between the left and right halves of the circuit if they were very very close together. In classical theory i think you can say that there would be interaction at any distance, but in the practical sense it would probably be very hard to measure even at closer distances because of the averaging effect.Will a quantum physics view change this? It may be argued that the effect will drop off completely at some distance but how far away that is depends on the granularity of the movements, and i would think that would be very very small and decreasing as the distance increases.Of course the two circuits need to be turned 'on' at some point in time. That means that there will be a much larger acceleration at first which means some interaction is almost unavoidable, but only up until the exponential part of the response dies out, and even though it only dies completely in the case of time approaching infinity, most of us would agree that we consider it to die out long before that in any practical case.What might be interesting is to consider the perfectly symmetrical case where both circuit are identical and both are turned on at the same time. The fields probably act like two balloons bumping into each other.One thing about all of this though is that any interaction does not depends on the wire connecting the two. It would occur with no wire as well, except there would be no current in any wire if there were no wire of course even if the two circuits were not exactly symmetrical, of course.This got a little long which happens sometimes :-)