Power struggle

[Enzo]

Geez, I hate to see a whole new section sit empty.

So I wondered: with all them electrons running to and fro, don't they sometimes run into each other?

[Ray Ivers]

Enzo,

Not really, I don't think - there's so many holes running around, there's plenty of room for all.

Not.

Sad to say, I still see this topic batted around at other BBS's (conventional current flow vs. electron - actual - flow). I think one really has to see the "light bulb come on" in someone's eyes when they first fully grasp the electrons-as-water analogy - along with the puzzled, blank stare that usually accompanies initial exposure to the "hole-flow" kludge - to truly understand why it's not just a meaningless semantical nit-pick, but often the difference between truly understanding/becoming interested and not understanding/regurgitating to pass tests, but that's just my $.02.

OK, $.01.

Ray

[Luijo]

Geez, I hate to see a whole new section sit empty.

So I wondered: with all them electrons running to and fro, don't they sometimes run into each other?

Since they all have the same polarity ( -), they should never collide but repel, IMHO.

[Enzo]

But in AC, they go back and forth, sometimes you'd think some of the ones turning back might bump into others that haven't turned around yet.

God knows I run into enough holes every day...

To be serious, no really, After 50 years of electronics, I think I have a grasp of it. To me it almost a zen thing at this point. When I was a kid, I realized that electrons flowing was the real deal. All we had was tubes, and it is pretty intuitive with them. But then and to this day, I think in terms of conventional currents. That positive supply is fighting to find its way to ground as opposed to all those electrons in ground fighting to find their way to that positive sink hole. In CC the arrows on the diodes point the right way. That alone is worth the price of admission. The water in plumbing analogy is just so very strong - better than most analogies.

The disparity never bothered me. I think one either intuits electricity or they just never get it. Electrons or holes are just crutches.

If you see a series of lights coming on in sequence - classsic chase lights - a dark bulb takes the place of a lit one as they move around. If you look at it, you see a light moving around the circle. You do not see a dark space moving the opposite way. They are not the same.

It is a joy to encounter someone who gets it, so you can then move on to explaining the electronics, as opposed to someone who can learn about circuits but never fully intuits it and so is unable to make proper inferences elsewhere.

[Ray Ivers]

Enzo,

Hey, that's great that you can easily see it both ways - I just can't. I guess I could never get over the fact that electrons actually exist and their flows have been observed, whereas IMO hole theory was basically created so existing textbooks could continue to be used.

If one can use one, the other, or both to understand - that's all that really matters!

Ray

[Enzo]

We all know how Santa Claus acts even though he doesn't exist. No really.

To me the reality of the physics is not what is on my mind when I delve into the systems. I never forget that electrons are moving around. Look at tubes. The physics is not a mystery. The cathode gives off electrons, and they flow to the plate. Even a solid state guy has to accept that in the CRT of his computer, there is a stream of electrons coming from the... get this...ELECTRON GUN, and they slam into the phosphor of the screen to make an image. I can't imagine someone who thinks that there are holes gathering on the screen and then leaping in a tight stream back to the cathode in the neck of the tube.

But when I am working on a circuit, to me, there is that positive B+ trying to find its way to ground. I know intellectually that is backwards, but in terms of troubleshooting, it is a convenient convention, and I am not confused by it. It makes ground the ultimate destination of everything rather than the source of all.

I find it a lot more useful to look at a B+ supply as a source of positive current that then fans out to various places, (Like the fresh water plumbing system.) than a ground full of electrons all streaming through various paths to collect at the first filter and rectifier. Though that would be very much like the sewer system, wouldn't it?

I think we can ignore holes until we get into solid state, then it is a matter of how the electrons get through the parts in P and N materials.

Maybe to me conventional currents is more like a series of voltage drops than real current. I look at a triode and see that electrons are flowing from the cathode to the plate, but at the same time, I see the series of voltage drops starting at the B+ node, then through tke plate load, through the tube, through the cathode resistor and ultimately to zero at ground. I doesn't confuse me, but I can see how it might baffle someone if I switched back and forth between the two views in a discussion of a circuit. I make a very conscious effort to watch how I put things in discussions here, in particular with someone just learning.

I have a local fellow trying to learn, and I throw around terms like ground and it confuses him. I mention a cathode is "grounded" through a 1.5k resistor, and he doesn't realize that "grounded" in that sense is not the same thing as "grounded" as in connected right to chassis. he would ask me a question like how can there be a voltage on the cathode if it is grounded. That sort of thing helps keep me sharp. he is right, I should be less cavalier with my terms.

Ultimately, if you understand the concept of signal flow versus DC currents, and consistently and systematically understand how the DC currents flow, I don't think it matters which convention you use.

[Enzo]

How about this: it is like speaking in terms of left and right on a stage, and at the same time knowing stage left and stage right.

I can imagine two of us standing in the house and discussing how the drums might look better a bit to the left and then writing down, "drums - stage right."

Sorta...

[Paul P]

I've been struggling for several months now, trying to get it. I think I'm now
pretty close. I think of positive voltage as sucking electrons out of the
ground. Or a least trying to. B+ is like a vacuum cleaner sucking air through
the plate resistor, which is like a straw. The tube acts like a container
connected to the straw. If the tube is not conducting the container is
sealed and the 'air' in the container is at the same vacuum as B+. When
the tube starts conducting it's like letting air (the electrons) into the
container, which lessens the vacuum (the voltage drops). If the tube really
opens up the vacuum will almost disappear since the vacuum cleaner can't
keep up through the straw. Once the tube shuts down the vacuum builds
up again (the voltage rises).

A coupling capacitor is like a tank with a diaphragm in the middle. Sucking
air out of one side (positive voltage on that side,) causes the diaphragm
to bulge in that direction which pulls some air (electrons) on the other side
into the tank. If the pressure varies on one side (AC signal) this will cause
varying pressure on the other side without any air moving through the
diaphragm.

The flow of air on the far side of the tank (the coupling capacitor) is
controlled by the following grid resistor (another straw).

The DC component causes an initial bulge in the diaphragm which sucks
a bit of air (electrons) through the following grid resistor but then things
stabilise. The diaphragm's position at this point is then the zero point for
subsequent fluctuations.

A negative voltage blows electrons back into the ground.

[Enzo]

Nothing wrong with those analogies. The diaphragm thing is an old often used one.

I think I have several ways of visualizing the functions of a circuit, and I don't have a problem in my own head switching between them as the needs warrant. The problem is in communication with others, then you have to be more consistent.

Outside the US they call tubes valves, and it is a very apt term. I think of the triode as a rubber hose for current, and the grid is like my fingers squeezing the hose shut. The more negative the grid, the harder I squeeze, until the flow is cut off.

As long as you realize there is a path for current from ground, through the cathode resistor, through the tube as controlled by the grids, through the plate load and back through the power supply, you will be fine. Ohm's Law - which I could not get through the day without using at least once - then tells you what voltages to expect.

[MitchK]

awesome thread, the analogies are really interesting and useful.

and a literal answer to the question is well, the closer an electron gets to another one the more force it takes to overcome the repulsion between the two right so you might think that well it would take a lot of energy to actually make two electrons collide but really, electrons don't really exist in any one place at anyone time for all intents and purposes, they are fields or waves of potential, so they are always interacting and in that sense constantly colliding, but at the same time never actually touching becuaes they don't necessarily occupy any space. If you shoot 1 electron a sheet of gold with two partitions in it, it will go through both of them at the same time!

here is an awesome video on the subject, that may or may not cause some peoples brains to explode haha

http://video.google.ca/videoplay?doc...e+wave+duality

[Enzo]

I won't explode on you. When I went off to college many years ago, it was as a physics major.

[MitchK]

thats awesome! I may have to pick your brain some more than I already do. and yea haha I was being kinda sarcastic. But it is a really good video for explaining it in layman's terms I think.

[Arthur B.]

Geez, I hate to see a whole new section sit empty.

So I wondered: with all them electrons running to and fro, don't they sometimes run into each other?

Since they all have the same polarity ( -), they should never collide but repel, IMHO.

Yes they do. Although as Luijo points out, they don't "collide" in the classical sense. The correct term for this sort of interaction is scattering.

[kg]

If you shoot 1 electron a sheet of gold with two partitions in it, it will go through both of them at the same time!

only if there's no one there to watch it.

[Enzo]

If a 100 watt amp is totally cranked out in the woods where no one is around to hear, does it still like totally rock, dude?

If a tree falls in the forest and no one is around to hear it, how do they know the tree fell down then?

While I enjoy discussing the real physics of it all, the original post was intended to conjure up an image of AC current where some of the electrons were turning back to reverse direction and bumping into the guys further back in line still going forwards.... Y'see...