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TheTooth · Post by **TheTooth** » Sun Apr 17, 2005 10:22 pm

vb_master wrote:I thought electricity flowed from + to -?

Electicity flows both ways at the same time. It's just easier to think of electricity moving from positive to negative for producing circuits. There have been the theories for both ways: conventional theory (positive to negative) and electron flow theory (negative to positive), but our current understanding of physics allows us to see that it flows both ways depending on how you look at it.

If you look at old cars from say the 40's you notice that the "ground" (the pole of the battery that's connected to the frame) is positive. This was the time of electron flow theory.

Niku-Sama · Post by **Niku-Sama** » Sun Apr 17, 2005 10:57 pm

dude....thats AC current.....were talking about DC

and besides even if it were AC, if it has no ground....err other connection, the electrons arent going to be flowing through it

well thats what i leaned from grabbing a cable not knowing part of the sheilding was missing on one of the wires...freaked me out but didnt zap me

Post by **SpongeBuell** » Mon Apr 18, 2005 6:46 am

yeah, electricity really does go from - to +. It is caused by a bunch of electrons stripped from atoms put together in one place. Like charges repel, and they try to get away from each other. The best place for them to go is to the opposite charge, which it is attracted to. This is the +.

THERE! I WIN!

TheTooth · Post by **TheTooth** » Thu Apr 21, 2005 3:20 am

damn i guess my Electrical engineering teacher/text book was wrong because you say so... and i'm not speaking of ac, that's totally different, it just constantly changes polarity: it flows in a sin wave rather than in a strait line such as DC current. I figured I wouldn't need to expalin this as it was like a 2 hour lecture in the class and i've heard it twice, but here it is in a nut shell as best I understand it (as the lecture was about 2 years ago and it wasn't a physics class).

I'm going to assume that any who is involved in this argument understands the very basic make up of an atom (electron shells and subshells as well as wtf an electron is for that matter) and understands something about how they interact with one another.

Let's say we've got one strand of coper wire, that wire is made up of several copper atoms all bonded together. Let's also say that we now hook that wire up to a battery. What that battery will do is introduce new electrons into the various subshells of the copper atoms.

The most simple way to explain this is to imagine that the elctrons are like marbles in a tube. Let's say that the electrons that are origionally on the copper wire are green and the new electrons from the battery are black. As we add black marbles the green marbles get pushed out of the tube. Add one black marble and one green marble gets pushed out the other end. It's not the black marble that get's pushed out it's the green marble at the other end of the tube. The black marble is now in the tube and if we added enough black marbles it too would eventually get pushed out.

Now apply that to actual atoms. As an electron moves from the battery it, basically, replaces an electron in the chain of copper atoms, which replaces the next one down the line and so on until the last atom at the end of the chain gets pushed out into the load device. Seems simple enough, but realize that in order for an electron to move from the battery and occupy the same space that an electron had just occupied in a copper atom there must be a spot open.

Let's call these open spots holes. Imagine that the chain of atoms is a horizontal line across your screen and the new electrons are coming in from the right hand side. For any electron from the battery to enter on the right the electron before it (on it's left) must have alredy moved and left a hole. You can follow this chain all the way to the left and see where the first hole started: on the very left. So as the elctrons move left the holes move right at an equal speed. otherwise the electrons would have no where to move to.

Therefore, electricity moves both directions at once. Electrons one way and holes the other way at an equal speed. Conventionally (what is normally taught), we think of electricity moving from positive to negative. As you know it is easier to diagram a circuit that way, and you can see that the negative polarity in most electronic devices is generally termed the "ground" (a term taken from electricians actually working with an earth ground) showing that the electroic engineer/s who designed the device used conventional theory to help in their design.

nos_slived · Post by **nos_slived** » Thu Apr 21, 2005 8:16 am

DC doesn't flow straight. It is in a wave, but it is a small wave and it is all above the 0V line. In your last paragraph, you said that it flows both ways because the holes go + to -. Well, we are talking about electicity, the flow of electrons, not the movement of sub-atomic particles.

Alchemist · Post by **Alchemist** » Thu Apr 21, 2005 9:24 am

nos_slived wrote:Well, we are talking about electicity, the flow of electrons, not the movement of sub-atomic particles.

You are making bold asumptions about what the word "electricity" means. From Wiki:

Electricity is a property of certain subatomic particles (e.g. electrons / protons) which couples to electromagnetic fields and causes attractive and repulsive forces between them.

What you are talking about is electric current:

A flow of electricity is called an electric current. A direct current (DC) is a unidirectional flow; alternating current (AC) is a flow whose time average is zero, but is not zero at all times. That definition of AC implies that the flowing electricity repeatedly changes direction. (Polarity and numerical sign (i.e. negative vs. positive) are additional terms for direction in this sense).

Unidirectional means in one direction, so then you'd be right.

TheTooth · Post by **TheTooth** » Thu Apr 21, 2005 1:05 pm

Iâ€™m not exactly sure what you're saying alchemist but they are using unidirectional there to mean on polarity. Otherwise, I agree with you.

Also, so far as I know DC hovers around whatever voltage it is, not necessarily the 0V range: if it is 10 volts of DC then it will be at 10V on the Y axis. I believe I've graphed enough DC voltages in my life to know that. If you want I can scan in pictures from "Introductory Circuit Analysis" by Boylestad Tenth edition. That and class lectures are where Iâ€™m getting my information.

Also, if DC moved in any sort of wave then digital electronics would not work. Analogue is simply defined by varying voltages, while digital is defined as constant voltages (very simply defined). Digital works by taking a constant voltage and switching it on and off. So, if DC were to move in a wave pattern it would fry more sensitive digital electronics.

I really will scan in pictures or give you direct quotes from this text book copyright 2003. I know it's two years old but electron flow theory is about 60 years old... I'm going to go with the two year old TEXTBOOK rather than the 60 year old theory taken from as reliable a place as the INTERNET.

But that's just me.

TheTooth · Post by **TheTooth** » Thu Apr 21, 2005 1:06 pm

sorry I read that wrong, I thought you said that, "DC hovers around the 0V line." Heh...

nos_slived · Post by **nos_slived** » Fri Apr 22, 2005 6:20 pm

TheTooth wrote:Also, if DC moved in any sort of wave then digital electronics would not work. Analogue is simply defined by varying voltages, while digital is defined as constant voltages (very simply defined). Digital works by taking a constant voltage and switching it on and off. So, if DC were to move in a wave pattern it would fry more sensitive digital electronics.

It does wave, but is only a few mV.