ECN Forum Forums Technical Discussion Electrical Theory and Applications Do electrons Oscillate?

Quote:
"I'm still grappling with WFO's 'holes' moving to the other end of a conductor! "

Personally, I always thought there were a lot of holes in that theory myself..........

Here's a crude analogy of hole flow. Think of a variation of "musical chairs" in which there is one too many chairs. A bunch of players and a bunch + 1 of chairs, players sitting in all but one chair. Frequently someone gets up and moves to another chair, then someone else does the same, and so on. There's always a minimum of one empty chair. The empty chair does not move, but from a distance the empty spot appears to move in opposition to the actual movement of the players.

Or, how about a bunch of 3ft diameter holes drilled in the surface of a frozen lake, with a tennis-ball floating in the hole, representing the nucleus. Next to each hole we place an "electron"; let's use a frozen pea. Now introduce a bunch of skaters. When one of them stops for a pea, the guy behind kicks him in the ice-hole.

Alan

....getting back on topic.....

Hole flow is actually just an extension of one of Newton's basics of physical law.

For every action, there is an equal and opposite reaction.

If the electron (negative charge) goes in one direction, the neucleus (which is now positively charged) goes the other.

Think of a capacitor charging. As all the negative charges stack up on one plate, the other plate is stacking up with positive charges.
The thing that bothers me about this "physically" is that (in my mind) the neucleus obviously cannot be moving to that plate or the capacitor would become a black hole of mass on one end and almost mass-less (if that's a word) on the other.

As to how much of a "I need to know this" piece of info this is, I think it is much more useful in understanding certain aspects of semi-conductor properties than electro-mechanical work.

Any thoughts on this that don't involve peas and ice?

I think holes are great because they give cover to the great old dead guys who:
1.) Got current flow wrong, always making us consider electron flow Vs conventional current flow.
2.) Drew our diodes backwards.
&
3.) Tried to help those of us not quite dead yet, to understand PNP transistors.

I'm still wondering if all those angels on the head of a pin are spinning or motionless, carry a charge or try to remain neutral.
Joe

Radar:
Not very far, indeed! I was astonished to find out just how slowly electrons travel in copper wire. It's:

(4.62 millimeters/second) per (volt per meter).

So, what the heck does that mean?

It means that if you take a piece of wire one meter long and connect a one-volt battery across the ends, the electrons travel at the rate of 4.62 millimeters (less than 3/16") per second!

If that doesn't sound like a lot of work getting done, consider that if our one-meter wire is awg-24 (0.5 mm), the current is over 12 amps!

The diameter of the wire doesn't matter. As the wire gets larger, the current goes up proportionally, but the velocity stays the same.

If, instead of a one-volt battery, we apply one volt RMS, 60 Hz AC, that Sharpie-marked electron travels only 1.4 thousandths of an inch in each direction.

Sort of...

Actually, a more correct term for electron travel is "drift," rather than velocity. Electrons are constantly zipping around at 1.3 million meters per second, the Fermi velocity, even at absolute zero. They're just moving in random directions, so there's no net current without an electromotive force applied.

Is that cool, or what?

This is a cool thread, it gets you thinking....


Dnk..

I have to admit that my knowledge of physics falls somewhere short of the term "Fermi Velocity". If I'm converting this correctly, this comes out to just a few hundred yards short of about 808 miles per second, a right snappy speed at that.

How do we balance that against the relatively slow rate of travel of current flow in an electrical circuit, measured at 4.62 millimeters / second / volt / meter?

One possible answer is a vast quantity of electrons drifting randomly, and within that a relatively few non-random moving electrons participating in current flow, leaving the overall appearance of relatively slow travel of current flow.

Another possibility, perhaps somewhat more likely, is again a vast quantity of randomly & rapidly drifting electrons, the whole sea of which is drifting slowly towards the positive pole of an outside force (and of course being replenished by the negative terminal).

Attempting some additional reasoning based on what John said earlier, in the one meter long sample piece of copper wire, we can reduce resistance by increasing bandwidth (larger diameter), and we get more electrons to flow (more pathways) but at the same constant speed. On the other hand, if we leave resistance alone at the original valus but increase the voltage applied instead, we end up with the same number of electrons moving but at a faster speed, twice as fast actually, effectively yielding more electrons per second flowing past a given point.

Kinda like on a freeway, more lanes at the same speed gives more cars per hour, same lanes but faster speeds also gives more cars per hour. Bandwidth verses speed.

Sure would be interesting if we could actually see this stuff working, heh?

Radar

I thinks it's time for a cold beer.

A beer?

How bout a 6?


Dnk....