# Thread: Question on electron flow

1. ## Question on electron flow

This just popped into my head and I realized... I have no clue whot the answer is. Not even remotely. I know the basic concepts of electronics and circuits and so on, but... yeah.

Let's say yeu have a circuit, nice simple circular one, electrons going around it along the path.

Then yeu break the circuit, cut a hole in it.

...How come the flow STOPS instead of falling out of the loop?

Srsly. The electrons somehow just 'know' that there's a gap now, despite that they haven't physically been to the gap to know this. Everything just STOPS.

They're not physically pushing each other through the circuit, and whot's more odd, is as soon as yeu reconnect it, they return to their standard flow, despite that there's nothing pushing them in either direction forcing them to do so.

How is it possible for this to occur O.o

2. Originally Posted by Katsuni
This just popped into my head and I realized... I have no clue whot the answer is. Not even remotely. I know the basic concepts of electronics and circuits and so on, but... yeah.

Let's say yeu have a circuit, nice simple circular one, electrons going around it along the path.

Then yeu break the circuit, cut a hole in it.

...How come the flow STOPS instead of falling out of the loop?

Srsly. The electrons somehow just 'know' that there's a gap now, despite that they haven't physically been to the gap to know this. Everything just STOPS.

They're not physically pushing each other through the circuit, and whot's more odd, is as soon as yeu reconnect it, they return to their standard flow, despite that there's nothing pushing them in either direction forcing them to do so.

How is it possible for this to occur O.o
Firstly, you're gonna have something causing the electrons to go around the circle, a battery for instance, it creates an electric field, that causes electrons to flow around the circuit.

Now, when you cut a hole in the circuit, the air stops the electricity from completing the circuit. The charge will build up on the end of the wire (wiki: St. Elmo's fire ), until it has enough energy to ionize all of the air between the gap. If you apply enough power, the circuit can easily arc, just like lightning does, it completes the circuit by jumping the gap.

Capacitors use this idea, they consist of two large metal plates, separated by a small distance, and they will charge up until they have enough energy to jump the gap.

The gap there is usually air, but you can place other more conductive materials in there, like a gas, or a metal. The material then acts as a dielectric.

I'm not sure whether the battery will loose energy by being connected. I'm guessing that it wont, otherwise a battery would loose energy constantly, which it does, but only because the chemicals inside it slowly break down over time.

And also, the electrons wont just leak off the wire, there needs to be a positive charge for them to go to, or at least something conductive. If you look at Tesla coils for example, they actually ionize the air in random directions and arc out towards anything conductive, for example, an ipod, a door knob... or you!

Are you trying to do something with this or are you just wondering?

3. Originally Posted by Katsuni
This just popped into my head and I realized... I have no clue whot the answer is. Not even remotely. I know the basic concepts of electronics and circuits and so on, but... yeah.

Let's say yeu have a circuit, nice simple circular one, electrons going around it along the path.

Then yeu break the circuit, cut a hole in it.

...How come the flow STOPS instead of falling out of the loop?

Srsly. The electrons somehow just 'know' that there's a gap now, despite that they haven't physically been to the gap to know this. Everything just STOPS.

They're not physically pushing each other through the circuit, and whot's more odd, is as soon as yeu reconnect it, they return to their standard flow, despite that there's nothing pushing them in either direction forcing them to do so.

How is it possible for this to occur O.o
The simple answer is that the electrons don't actually "flow" around the circuit (or rather flow really really really slowly). What happens is that the potential difference of a battery (or any source of electromotive force) creates (a rather complex) electric field around the loop of the circuit (let's say a single light-bulb is in the circuit to keep things simple).

The electrons, without a potential difference across the bulb, are just giggling around, but on average there is no motion to the right or left. When there is an electric field due to a potential difference, the electrons are pretty much still just giggling around at random, but have a very slow "drift" in a particular direction. That is on average the whole mess electrons has more charge moving in one direction rather than the other.

The speed of "drift" is about 10 micrometers per second on average. That is 1/100th of a centimeter per second. To travel about 5 cm (about 2 inches) it would take 500 seconds or about 8 minutes. That makes about 4-5 minutes per inch...I've seen snails move faster.

The potential difference however is communicated like a wave (note how a wave can travel in water without the water actually traveling with it) and happens nearly instantaneously. Then the electron all along the wire start to drift at approximately the same time, so the current is about the same on average through out the light-bulb circuit.

When you open the circuit, the potential difference is no longer across the light-bulb. The whole bulb and the wire connected on one side is at the same potential. The wire connected to the other side of the open is all at another potential. This change in potential difference is communicated almost instantly to all parts of the circuit, and the electrons stop drifting. So on average the electrons leaving the loop through the open will be the same as those entering.

4. Thanks very much, I knew I'd forgotten some important stuff from my electronics course... probably because the course was a joke at best. No equipment, every class was 50/50 either "watch a movie day!" or "have fun on the internet day!".

Shame, I took that class so I could repair my headphones originally, didn't learn much of anything in it... learned more from wikipedia XD

But yeah, that helps alot, thanks for answering that =3

5. It's because they are attracted to the protons in the nucleus of the metal atoms. The electons don't care which atom they are close to, as long as there is one. While the circuit is complete, they can hope from one atom to another and go all the way round. The moment the circuit breaks they would have to fall of the atoms to continue. The attaraction between the electron and the proton stops that from happening.

6. Originally Posted by Katsuni
Thanks very much, I knew I'd forgotten some important stuff from my electronics course... probably because the course was a joke at best. No equipment, every class was 50/50 either "watch a movie day!" or "have fun on the internet day!".

Shame, I took that class so I could repair my headphones originally, didn't learn much of anything in it... learned more from wikipedia XD

But yeah, that helps alot, thanks for answering that =3
Most classes you're better off teaching yourself via online

7. Originally Posted by tawanda
Most classes you're better off teaching yourself via online
Yeah, this is true, but this class was *REALLY* bad...

They'd just built a new school but hadn't gotten ANY of the electronics equipment; they ditched all the old stuff, but got nothing new, so there literally was nothing to work with, just a standard computer lab.

Furthermore, the teacher was obviously clueless; he had NO idea whot he was doing. If yeu asked a question, the answer was either to look it up online, or he'd go into the other room next to him to ask the teacher in there O.o;

About every 2nd class (literally every other class) we'd watch a movie instead of doing any work...

The work we DID do, was limited to "here's a piece of paper with 5-6 questions on it, write in the question word for word into google, and write the answer yeu get down word for word".

That usually took about 10 minutes out of the 1:40 classes (think they were that long, they were abnormally long anyway) and the rest was just wasted time.

I spent alot of time on howstuffworks.com myself there, and learned far more from that than from the class >.<

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