current flow and electron direction

Here is something that I've been trying to clear up in my own head... Is the flow of electrons always in the same direction as the current flow? I know that this sounds really elementary but I often see some tech info written as if they were actually opposite. Arrows pointing current flow in one direction but hearing my old electronics teacher telling the class that the actual movement of electrons was in the opposite direction. Hmm... Can anyone give a clear explanation of the difference OR are they one in the same???

Thanks

Mike

your talking about electron flow verses hole flow?

electrons go from negative to positive while the holes flow the other way

basicaly the hole is created as the electron travels from negative to positive

The problem stems from the early electronics geeks who mistakenly thought electrons flowed from positive to negative. (The "water in a pipe analogy.) It actually flows toward the charge, since the electrons themselves are negatively charged.

Mathematically they're equivalent, so for a long time people stuck with the older convention. Many people still do.

I've always found this to be kind of annoying. A circuit designer writing about his/her circuit might say, "then current flows through R11 to ground", which intuitively makes me thing the voltage must be negative with respect to ground.

Personally, I wish they would have corrected that convention early on and stuck with it.

It's just a convention---long before the discovery of the electron, dating back at least to Benjamin Franklin.

If we lived in an antimatter world the current flow and vacuum charge carrier (positron) flow would be the same.

If antimatter weren't so reactive and expensive to make we could have tubes made of it and use them in complementary circuits.

It also depends on the situation; most engineering books stick with the conventional current flow. It doesn't really matter so much, though, as long as you are aware of which method you're using, and stick with it (not combining them). I guess what I'm saying, is that, after being exposed to both, they can be equally confusing, in the right circumstances! (Hmmm, positive ground?) :grin:

Electrons flow opposite to the current flow.

In fact, it would be more precise to say "electrons tend to flow opposite to the current flow".

When viewed as particles the electrons inside a conductor are bouncing around in all directions in a sort of Brownian random walk. This is because everything with a temperature above absolute zero thermally vibrates. When a potential is applied across the conductor the electrons have a higher probability of moving towards the more positive end - the bigger the voltage the higher the probability. Nevertheless, they continue to bounce around in all directions.

The details of electron flow isn't very useful information for most electronic design; unless you're actually designing semiconductor devices or submicron integrated circuits.

> the flow of electrons always in the same direction as the current flow?

Who cares???

The only place we REALLY care is in thermionic vacuum tubes. There we know current is carried ONLY by electrons, and they flow up to B+. Even so, most napkin sketches use arrows pointing down. It really makes no difference.

OTOH, in gas-tubes, there is a huge flow of positive ions. Electrons are still the main current, but the positive ions break-up the electrons' fields, allowing MUCH more current flow than you can boil off a thermionic cathode.

And in solid-state, positive and negative "charges" have about equal weight. The concept of "holes" seems empty, but holes in electron-rich solids are very effective current carriers. Not just in doped silicon: copper wire has "holes" "moving" backward from the electron flow. The total number of electrons in a hunk of wire is preserved constant, yet "something moves". We could just as well have decided to count copper holes when measuring current.

The generally accepted equations needed a sign-convention. At that time the nature of current flow was not understood at the particle level, and we now see that either positive or negative charges, or both, may be useful in different devices.

> mistakenly thought electrons flowed from positive to negative.

No, they didn't know what electrons were or which way they flow. They did know there were "two types" of electricity: some things cling and some things repel. The sign-convention arbitrarily picked one polarity to call "positive" so the math would work out right. It later turned out to be significantly easier for some devices to isolate and use negative charges than positive charges.

> designer writing about his/her circuit might say, "then current flows through R11 to ground", which intuitively makes me think the voltage must be negative with respect to ground.

Do not read too much into technical writing. Sometimes it is pedantically perfect (W. Marshall Leach tends to get it right); very often the writer has great understanding of napkin sketches and general circuit balance, yet a sloppy way with words.

However assuming the writer is using the mathematical convention for current sign, then "current flows through R11 to ground" implies that the un-grounded end of R11 is positive. Even if R11 is the cathode resistor for a vacuum tube. Many tube-heads insist that current flows plate to cathode, even though "we know" the electrons flow cathode to plate.

As bcarso says: if you are from another planet (some members here may be), then your results may be different. Send your excess P-type anti-vacuum tubes to earth so we can make complementary pairs.

Benjamin Franklin
Was right and I do not care if it is considered wrong today.
Benjamin Franklin said voltage flows from the positive to the negative.
So it flows into ground. And on your schematics the silicon diodes actually work. The voltage flows in the direction of the arrow on the diode.

Using that method keeps me sane.

[quote author="adrianh"]Benjamin Franklin
Was right and I do not care if it is considered wrong today.
Benjamin Franklin said voltage flows from the positive to the negative.
So it flows into ground. And on your schematics the silicon diodes actually work. The voltage flows in the direction of the arrow on the diode.

Using that method keeps me sane.[/quote]

Since when started voltages to flow?

Voltages dont flow, currents do, voltages indicates
only potential differencies.
:guinness:

As bcarso says: if you are from another planet (some members here may be), then your results may be different. Send your excess P-type anti-vacuum tubes to earth so we can make complementary pairs.

Click to expand...

Interesting, i wonder what a quantum mechanic theorist whos
into string theory would say about currents and flows in antitubes ! :grin:

That was PRR who said that.

just trying to make it very simple here.

Yes that is right.
I just think of flow from + to ground.
and yes that flow is electrons (or holes) depending
on the direction.

Yes the EMF is the force in volts

Thanks guys! This clears up things up a lot! Thanks!!

mike

Do yo want to know the REAL reason behind this mess?

After they found out their mistake on current direction, it was too late. They would have had to re-write millions of text books across the world. Too much inertia. It would be like telling the world to change from PC to Apple. That is why engineers and physics classes still use the wrong way.

I have heard some engineers say that it is actually a bit easier to design with the wrong current direction.

The hole is just a concept developed for PNP transistors. Minority current carries. Who's the idiot who came up with that confusion? Was there a monkey bouncing on his typewriter while he was a asleep? Who needs holes anyway.

Well, once in a while! :razz:

quote: "Was there a monkey bouncing on his typewriter while he was a asleep? Who needs holes anyway.

Well, once in a while!"

A friend was taking his physics pHuddy oral exam, which involved semiconductor physics, and had prepared a long joke that ended in the punchline from A Day in the Life: "Now they know how many holes it takes to fill the Albert Hall."

No one laughed.

I like doughnut holes.
Is that the same?

Let me guess: you don't get out much?

I have an entire book devoted to the deep philosophical status of holes.

I have a lot of books.

Most of the ho's I've met were minority carriers.