Say a word on Conventions !

[ElectroNewby]

I learned that electrons are going to the positive (+).
The electron leaves creates a "hole" which goes the other way.

So far so good. Electricity goes from - to +

Buuuuuut... I start college and BANG. Nope. Not good. Electricity goes from + to - by convention after an old war on the way it goes.

I rather know the real physic way of how it is going.

Am I going to be lost in my course if I keep thinking of the "real sens" it goes ?

I'd like to see your opinions on this convention, and any other.

I think it's not going to be a big deal in the end of the day!

 

[dknguyen]

Sucks but you get used to it. And in the end it's just a matter of mathematical convention...for the most part. They're gonna throw so much math at you that you probably will learn how to use the equations before you figure out what is physically happening.

And you'll soon see that often the physics is so in depth that you can't focus on the low level physics as much when you work with it or you lose sight of the actual application. So the convention being backwards of the physics doesn't trip you up as much as you'd think. It does rear it's ugly head occasionally though.

 

[Nigel Goodwin]

It makes no difference whatsoever, just ignore it.

 

[JimB]

Conventional current flows from +ve to -ve

Electrons flow from -ve to +ve

Get used to it, accept it, move on.

JimB

 

[ElectroNewby]

So in the end, it won't lead me to errors when doing exams ?
I connect think from - to + you know... cathode to anode. Are all the names reversed then?

 

[Sceadwian]

Basically assume + to - conventional current flow in all situations unless it's specifically stated that electron flow is what is being refereed to. I think the biggest thing to be wary of is physics, I've run across a lot of physics material that defaults to electron flow. And no the names do not reverse, the only thing that changes is basically the sign of the current flow, everything else still works out just fine mathematically. I had big problems with electron vs conventional flow for a long time.

 

[dknguyen]

Chemistry also defaults to electron flow.

Cathode and anode do not change. However, the direction that current flows between them is reversed in chemistry vs physics (and electronics). That's because in chemistry you are looking at how electrons flow inside the battery while in physics and electronics you are looking at how the current flows outside the battery. So outside the battery electrons (holes) are actually flowing from cathode to anode (anode to cathode), but inside the battery the electrons (holes) are going from anode to cathode (cathode to anode). The names do not change, the direction of flow does, however because of the internal vs external perspective.

When there is a schematic of any kind, I assume conventional/hole flow unless otherwise stated. In all other cases I assume electron flow.

 

[Sceadwian]

Chemistry is even more complex than simple electron flow because flowing ionic compounds are charge carriers in a liquid as well and their actual physical movement is massively important.

I personally detest the entire concept of hole flow, holes do not exist they are voids in the conduction/valence bands of an atom and I think referring to them as an object or as something that moves is the primary reason conventional vs electron flow is so confusing no hole EVER moves they do not exist, electrons move into and out of spots that are called holes though; in my opinion it's a crime against common sense that they're given the guise of a physical entity. I'd fight more against the use of conventional flow but it's pointless. It's easier to just note that conventional current flow is in the opposite direction of electron flow and be done with it.

 

[ElectroNewby]

Why haven't they set the score straight for everybody ?

If I think that electrons are attracted to the +, they will try to teach me the contrary ?
This is bad, somehow..

I was messed up when I had to indicate the flow of energy in a simple citrus-battery the other day.

Zinc leaves electrons in the citrus to ride their way on the Copper (copper accepts electrons right ?).

Also, I think of electrons as frequencies, and not little bubbles floating around a proton... It makes more sense to me that current is not little bubbles traveling fast but instead a frequency of given intensity and other measurable thing I still don't know.

I'm a bit confuse because I learned the chemical process.

So a question; Is a cathode still the negative on a battery or is it the positif disguised with the cathode name, OR a - sign while being a +

Holy crap.... I think I'll get a bit mad when doing my first homeworks

 

[Ratchit]

ElectroNewby,

I learned that electrons are going to the positive (+).

That's right. Electrons are negative charged, and are attracted to the positive terminal.

The electron leaves creates a "hole" which goes the other way.

That's false for a wire. There are so many negative charges (electrons) in a wire that a hole cannot possible exist without being neutralized immediately by a electron. Holes can exist in semiconductor material where electrons are relatively scarce.

So far so good. Electricity goes from - to +

What kind of electricity? Protons and positive ions do not.

Buuuuuut... I start college and BANG. Nope. Not good. Electricity goes from + to - by convention after an old war on the way it goes.

Do not confuse a mathematical method with the real direction of a charge carrier.

I rather know the real physic way of how it is going.

And you easily can, but don't apply that method while doing calculations.

Am I going to be lost in my course if I keep thinking of the "real sens" it goes ?

You will be confused, not lost. See below.

I'd like to see your opinions on this convention, and any other.

Read on.

I think it's not going to be a big deal in the end of the day!

Not if you do it right. Otherwise you will be wrapped around the axle.

Like so many nubes, you start out by worrying about what the polarity of the charge carrier is. Intuitively that makes sense, but it really leads to confusion. Most of the time you don't care what the real physical direction of the charge carrier is anyway. So to do it right, you stick to a standard mathematical convention. You mathematically assume that the charge carriers are of a positive polarity, flow out of the positive terminal of voltage source, and return to the negative terminal. You make all your calculations assuming that positrons or protons are the charge carriers. This is how the electrical equipment and product manufacturers mark their products. I am referring to ammeters and diodes. The arrow on the diode points in the direction of positive charge carriers, and the ammeter shows a forward positive deflection on the + and - terminals. To continue, you do your calculations and receive a quantity of amps for a circuit. That is your mathematical answer, and usually you are finished with the problem. But if it is really necessary to know the physical direction, then you look at the charge carrier's polarity and reverse the direction if the charge carrier is negative. So by not worrying about what the polarity of the charge carrier is at the beginning, the problem simply becomes a plug 'n chug exercise.

Ratch

 

[ElectroNewby]

Hey, thanks a lot for all the explanations !

I decided to "forget" everything I learned in order to learn accurate calculating. Its gonna be my job so I better not worry about the quantum size, chemistry will be a past-time. About the part on the semiconductor, it is actually where I learned about those holes, on a semiconductor lecture (Berkley on YouTube).
It was interesting but I'm not going to go into microelectronics.

When I said electricity going from - to + I meant electrons.

 

[MrAl]

Chemistry is even more complex than simple electron flow because flowing ionic compounds are charge carriers in a liquid as well and their actual physical movement is massively important.

I personally detest the entire concept of hole flow, holes do not exist they are voids in the conduction/valence bands of an atom and I think referring to them as an object or as something that moves is the primary reason conventional vs electron flow is so confusing no hole EVER moves they do not exist, electrons move into and out of spots that are called holes though; in my opinion it's a crime against common sense that they're given the guise of a physical entity. I'd fight more against the use of conventional flow but it's pointless. It's easier to just note that conventional current flow is in the opposite direction of electron flow and be done with it.

Hi there Scead,


A 'hole' is a very deep issue in philosophy isnt it. Whether or not a hole really exists is a very hard thing to define. Is it physical? On the one hand, when you see a deep hole in the ground there is nothing in that space, yet when you are walking you are aware that 'it' is there and you avoid it like the plague. A hole is made up out of a lack of something else. It's a view where we observe an entire 'map' of everything there is, and when something is missing in a given area we have to acknowledge it somehow. If we have a fence that goes completely around the front yard and there is no gap, we might say there is no hole in the fence. If someone drills a hole so they can see through, how do they see through if there is nothing different about the fence in that area.

In the solid state devices it's hard enough to figure out what is really there anyway, is it an electron, and if so, where the heck it is really? Thus we end up with negative charges and positive charges. If we call an electron negative yet we arent sure what the electron really is, why not call the lack of one positive and take it from there.

To get even stranger, a hole in the ground has air in it whereas the ground itself has much less. A hole in the moon supposedly according to the latest theories has some particles popping into and out of existence, so there is something there too. The hole is therefore made up of particles too just like the moon soil. It's a strange thing to talk about.

 

[MrAl]

Hello again,


Electrical current flow depends a lot on what theories you are working with. With some theories you'll be saying that the flow goes from the negative electrode through the circuit and then to the positive electrode, while with other theories you'll be saying the opposite.

The nice thing about 'conventional' current flow (from the positive through the circuit and then to the negative) is we dont have to keep track of the sign. This is more convenient than always having to deal with a sign.
For example:
E=I*R
but if we had to deal with the sign all the time we'd have to write:
-E=-I*R

So we can see it makes life easier sometimes. The same works better with control theory too where things work simpler with conventional flow.

The only way to deal with this duality is to learn how both systems work and use whatever is most appropriate at the time with the given context. Regardless what system you like best, you'll need to know both systems. The only real convention is that there is no convention as it always depends on the subject context.

 

[MikeMl]

I have worked with devices where the charge is being carried by a beam of positively charged Ions. I'm not confused by that. You shouldn't be confused when you encounter a circuit where charge is being carried by the movement of negatively-charged electrons... In both cases, the net (positive) charge moves in the same direction...