Wow! You're making me work here to "requote" your comments in quotes but, I think I've got it.

As I understand it, electrical resistance comes from two things. One is the number of electrons available for current flow (cross sectional area) and another is the length of the conductor (the cumulative impeding aspects) and the ease (or reluctance) that a material exhibits in releasing it's valence electrons.

Now, that raises yet another, related issue. There is a phenomena that applying a magnetic field to some materials doesn't change the resistance but, it does change the rate at which a signal can propagate along the material (it's called a magneto-restrictive material). I used to have a delay line that worked that way and I sure wish I knew whatever happened to it! It was really neat to play around with. I don't know that (or if) that effect changes the electron drift rate at all.

 

Starting a new thread - written like a textbook, perhaps with the name "Compilation of Electron Velocity Thread," would have several advantages - including avoiding repeats of the same theories and analogies, making it easier for new members to read the thread, and being a good review for editors. I can't think of how this would conflict with the purpose of Electro Tech Online. Editing posts in this new thread could involve quoting the entirety of the previous post and explaining editorial changes to the previous post in brackets. Someone would have to develop editing rules and place them at the top of the first post.

 

hi,
Of course all our theories are based on Bohr's model of the atom.!

Magentostrictive coils were once used in computer memory delay lines.

Once you start thinking about electron movement a number of effects seem to make more sense, like resistance, inductance and magnetic fields around the conductor.
Also why semiconductors exhibit switch on/off delays, reverse current decay times of diodes, Hall effect etc.


Hi Jason,
Why dont you start the thread you mentioned.?

__________________
Eric " Good enough is Perfect "
I will NOT answer PM's requesting technical help, please use the Forum
PIC tutorials: Nigel's www.winpicprog.co.uk/ Bill's: www.blueroomelectronics.com/

 

Rules for the thread could be that you have to quote the last thread posted, show all editorial changes in brackets, describe all editorial changes in double brackets, and note the date of all posts copied and pasted in double brackets. Can anyone think of any other rules? It could be like Wikipedia, except with fewer rules.

 

Well...we could all be required to type only left-handed....

There seems to be a natural propensity for threads to develp a "life" of their own after the initial spate of, on-topic posts. I can't speak for the masses but, I often learn more from the snags and runs and pills and loose stitching (and other corny thread-oriented analogies) than from the original topic and posts.

 

Hi Eric,
hmmm...., so it is the electric field that energies the device (say an LED ) causing it to function "almost" immediately and not the physical flow of electron, but then why a P-N junction transistor works so faster ? if the same phenomena of electric field or the gradient is applied to it (and I believe it is so as the P-N junction is also a conductor, I mean it conducts less or more as more the depending upon applied voltage ) then why they explain us with electron shifting in to holes and all that ? Is this because this shift ( even it being in the order of inches/hour ) responsible for the gradient ?

__________________
CHRIS

 

Let me butt in here...

Well, I can see what you are saying but, it doesn't change the physics of it. Let's go to your PN junction (although it could be any conductor). In a PN junction you think of electron flow or hole flow but, in fact, it's always electron flow (just as in a metal conductor). "Holes" are simply voids and have no energy but, they can be used as a mechanism to move electrons.

You state it exactly when you talk about the potential gradient. That's the key because it identifies that the electrical field extends accross the conductor and the influence is felt in all parts of the circuit.

As you inject electrons into the PN junction (or wire) they migrate across it slowly, doing work as a result (operating a motor or a computer or a microwave oven, etc.). But, the electron losing energy in your CPU is not the same one as being supplied, at that moment, by the power supply. But, it is one that's being influenced by the electron coming out of the power supply (and vice versa...ie: the electron at the power supply terminal is being influenced by the one in the CPU, trying to keep the current constant in all parts of the circuit).

The influence of the electrons around the circuit happens fast but not instantly. In a wire or semiconductor it happens at some percentage of the speed of light. The transistor can thus operate rapidly even though the electrons themselves move slowly.

Going back to the water hose analogy, if you modulate the water pressure at the tap rapidly, that modulation will be felt at the nozzle end...not instantly but, at the speed of sound through water...even though the actual water molecules from the tap are still just a fraction of an inch from the tap. Eventually, those molecules will migrate along the hose and exit the nozzle but, not until a lot of cycles of the modulation have been transmitted along the hose first.

Regardless of how the water is modulated or varied, ulitmately the hydro power is the actual average flow of water from the hose...and, so it is with an electrical circuit, except with electrons rather than water.

PS: Yes, I know that som consider "nothing" to also have energy so, I mentioned the semiconductor holes as having no energy of their own generically.

 

Hi crashsite,
I got that, it is the same as I understood but just needed fine confirmation thanks, and I also thanks to you too Eric,
BTW: HOLES is the term used to represent the absence of electron, nothing physically exist, I had rad in an instrumentation book where the author explains the definition of THEORY, it says that any scientific theory is just the MOST SUITABLE IMAGINATION through which we can explain the lows of nature but, it is not necessary that things should actually work as the THEORY explains it, Think of that famous Large Hadron Collider experiment where they are still trying to find the lost 70% of universe while we still use the basic gravitational lows for calculation even when they are largely inappropriate at cosmic level, I WONDER THEN WHAT IS THE ULTIMATE SCIENCE AND TRUTH !

__________________
CHRIS

 

hi,
The LHC had to been shut down the other day, helium leak into main vacuum ring.
Could be down for 12 months, it has to warm up from -270C before they can fix the leak, then recool .

It would be an ideal topic for a conspiracy theory.!

__________________
Eric " Good enough is Perfect "
I will NOT answer PM's requesting technical help, please use the Forum
PIC tutorials: Nigel's www.winpicprog.co.uk/ Bill's: www.blueroomelectronics.com/

 

Are you worried that this new thread would detract from this one? I don’t think that it would. You wouldn’t be required to participate in the new thread or type left handed. However, you are welcome to start your own thread in which people have to type left handed. Even If you knew how to develop a left-handed keystroke pattern recognition program, I don’t know that detection would be legal!

 

It would be the honor system....

 

Yes. I have a pair of 25 year old lamps with 10 foot cords in my living room running from 60Hz AC. I am secure with the fact that these wires still contain 99% of the same electrons that were in the copper when it was refined. The net electron velocity of 25 years of moving back and forth in the wire is zero, therefore the net change in electron position is also zero.

 

I didn’t realize that you had come up with a realistic rule. So far, I’m the only one who has voted against it.

 

Well, I think the bottom line is that electrons really do carry a lot of "punch". When they can move so slowly and still have such power make you think...okay...it makes ME think...of the posibilities of trying to tap into that energy in novel ways. Unfortunately, like a hack science fiction writer, I can see the possibility but, not the realistically attainable solution.

 

I’ve thought about natural gradients that might have or be converted into – and I’m not sure if I’m using this word correctly, an electromotive force. I haven’t thought of anything besides nuclear power, solar power, wind power, wave power, tidal power, geothermal power, and hydropower sources (documentation source at Wikipedia at http://en.wikipedia.org/wiki/Power). If you haven’t already heard, click here to see the New Sony Bio-Battery that Runs on Glucose: http://www.youtube.com/watch?v=gl3Yn-BPWw8. And here’s an example of a biodiesel project that could turn a generator: http://www.league.org/league/project.../Biodiesel.pdf.