Which direction does current flow?

So the Answer based on TED’s empirical evidence…

“Which way does current flow?” → Whichever way it can.

Bingo

ReverseEMF: Holes, as mentioned above, are conceptual charge carriers. They don't exist as a physical entity

You'd need to define "physical entity" fairly carefully to make that claim watertight, and probably lose the baby with the bathwater in the process. To a semiconductor physicist holes are very real...

To a semiconductor physicist holes are very real…

The are, they even have mass, which means the electrons in certain circumstances, have negitave mass. That means they are repelled by a gravitational field.

So go and patent your anti gravity machine now.

MarkT: You'd need to define "physical entity" fairly carefully to make that claim watertight, and probably lose the baby with the bathwater in the process. To a semiconductor physicist holes are very real...

Yes, holes are real, in the sense that a hole in the ground is real. If I try to set a flower pot on a "hole" it will not be supported, and I can fill it with water. It's an absence of dirt defined by the dirt around it. But, if I dig a hole next to it, and toss the dirt I dig up, into the previous hole, the hole will appear to have moved. But did it?

I can conceive of a model where holes in the ground "move", and it may work for certain physical systems -- like, maybe, some sort of "outback whack-a-mole", or stop motion animation where the hole becomes a character. But, the model falls apart if I actually try, on hands and knees, to shove the hole around the ground it's dug in.

If I try to actually move a hole in a crystal lattice--the lattice will shatter. The hole doesn't move, but it's useful to conceive of a model of it moving. But, that's all it is -- a model! And any physicist is deluding him/herself if they believe holes actually move. Believing models are real is a trap that even scientists fall into, and a trap that limits their thinking in a way that can hinder innovation.

And to make this crystal clear [pun?], I'm NOT debunking holes, I'm pointing out that the idea that holes actually move is a delusion, in the same way, anthropomorphising an android is delusional.

MarkT:
You’d need to define “physical entity” fairly carefully to make that claim watertight, and probably
lose the baby with the bathwater in the process. To a semiconductor physicist holes are very real…

Agreed. All these ‘physical’ things we see today appear to be formed by some forces (or whatever they call them which scientists probably don’t know the origins of, or how they exist etc). Those forces (or something) somehow form (or give us the impression of) things/entities/objects that people are able to define through observation, or theory, or measurements etc… what appears to be physical definable things, but are a result of ‘forces’ (or something, which themselves aren’t understood in terms of what they are, where and why.) Eg… these forces somehow combine to give impressions of ‘electrons’, ‘holes’, ‘rocks’, ‘wood’, ‘atom’, chemical ‘molecules’, electric/magnetic fields etc. So at the base of it… if OP is talking about current, or charge flow… it’s sort of like talking about how the forces (probably in some matrix pattern across our universe) bans together to give the impression of an ‘object’ or some lumped things moving.

So… as long as we define something clearly, and as long as we agree upon following particular definitions, then this helps to avoid issues with the communication.

Southpark:
Agreed. All these ‘physical’ things we see today appear to be formed by some forces (or whatever they call them which scientists probably don’t know the origins of, or they exist etc). Those forces …

I wasn’t saying holes are not real – just that they don’t really move. But, I see my error. : I got my wording wrong. :wink:

I wasn't saying holes are not real -- just that they don't really move.

Of course they move, how else can they have a mean free path?

Grumpy_Mike: Of course they move, how else can they have a mean free path?

What, exactly, is moving?

ReverseEMF: What, exactly, is moving?

The hole.

Grumpy_Mike: The hole.

You're funny!

I am also a physicist.

ReverseEMF: I think you're confusing current flow in a conductor with current flow in a semiconductor.

  • Conductor: Movement of free electrons [a property of metals].
  • Semiconductor: More like what you're describing [a property of specially doped semimetals or more exotic alloys].

Yes. You are absolutely correct, I am speaking of a semiconductor. Of course, nearly every (non-super)conductor has some semiconductor characteristic. "Free" electrons are not perfectly mobile in a conductance band. For a conductance band is not a band at all, but closely overlapping high energy orbitals in a close packed array of atoms. The electrons need to jockey for position, because, although there are a lot of states, Pauli still applies. In a piece of wire the mass of the electrons crawls along many thousand times slower than the movement of the charge, aka the current.

It's within this jumble of buzzing electrons that the holes exist - they are unoccupied orbitals.

Chris is right about that. Eg… a parallel plate capacitor. During the charging and discharging stages, the electrons don’t move across the ‘gap’ from one side of the plate to the other when a voltage source is applied across the two plates.

There is no electron movement across the plates of a capacitor. When an AC signal is impressed across the capacitor, there is the flow of electrical energy. Flow of electrical energy involves the flow of current. This is Maxwell who introduced the concept of displacement current which flows across the capacitor plates due to change in electric flux to enable energy flow. (it = ic + id = conduction current due to carrier + displacement current due to electric flux change)

Grumpy_Mike: The hole.

I think he was asking for a definition of what "moving" really means rather than for the thing that is moving.

All this talk of holes or absences of electrons moving reminds me of a nice Terry Pratchett quote:

Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it.

:)

I love it when we take a subject like this and run with it...

I see it like the small trees I just planted in my yard.

The holes we are talking about are an atom in a lattice that has the LACK of one electron.

If there are 3 holes in a row, and the first one acquires an electron, there are 2 'holes'.

If the electron moves from hole 1 to hole 2, the hole 1 reappears.

If I put a tree temporarily in my first hole, there are two holes left.

If I move the tree to the center hole, there are two holes left.

So I can propagate holes. Trees can drift in one direction, and holes (the LACK of a tree) can propagate in the other direction.

OK, enough... I gotta go water those trees.

Grumpy_Mike: The hole.

I still maintain that the hole doesn't "move". Holes merely appear and disappear--as electrons occupy/vacate orbitals. Movement is a "useful delusion", in the same way cinema is. The appearance of movement on the screen is a phantom created by the mind. And, in fact, the so called movement of holes isn't even seen. That's why I used the word "delusion" in association with hole movement, and illusion in terms of movie *movement. *

In fact, isn't it true that there isn't, even, a physical hole--as in some stationary pit surrounded by boundary defining electrons? I mean, in reality, it's just one less probability cloud, around the nucleus of an atom, right? So, to call that a hole, is even more delusional, right? And by delusional, I mean, a model, and not an actual thing. A useful delusion.

So, hole, is a model for a missing electron cloud -- which doesn't really resemble a hole. And, any movement of this phantom entity, is only conceptional. In an electric field, they do seem to move, but not really -- but, it's useful to think of it that way.

And, consider this: locking yourself into a way of thinking, based on an accepted model, makes it difficult to advance the field. Einstein was able to discard models and think beyond them. Because he was able to think beyond Newtonian Physics, he knocked Physics on its ear. The history of the conceptualization of the atom is another good example. If physicists had decided that the plumb pudding model was the end-all-be-all, science would not have found its way to orbitals and the to the current, very strange, model of the atom -- and it's still a model!

But, I'm not a Physicist. :P

terryking228: So I can propagate holes. Trees can drift in one direction, and holes (the LACK of a tree) can propagate in the other direction.

The holes themselves are still pretty firmly in place... it's just that one appears when you take out the tree, and it disappears when the tree is placed in one. The location of where a hole is moves. The hole itself doesn't.

wvmarle: The location of where a hole is moves.

How do you know it's the same hole?