How does the current flow?

[AndreeU17]

So i know this is basic, but i'm in my 5th quarter of Electrical Engineering, and i havent really grasp the ideal way the current flows. I have teachers telling that current flow from the (+) side of a battery or even the (-) side of the battery.

But i was reading that, Electrons flow in the direction of the protons to attract. If thats the case then wouldn't the flow of current travel from the (-) lead into the (+) lead?
Lets see a simple example:

So would current flow from the top (+) into the resistor (Which will control the amount of current to flow into the LED then back into the (-)? Or would it be vice-versa? if thats the case then shouldn't the Resistor be before the LED if the current flows from the (-) of the battery?

I understand the life of atoms and electron, etc. Just a bit confused as to how the electric current actually flows? I have had bigger schematic, that contain both VCC and negative VCC, etc. They get more elaborate and crazy, so all i want to know is how does current flow? it helps me visually label what component the flow of current will hit first, or estimate the first contact!

 

[davenn]

before it was known that electrons existed and that they were the charge carrier
Current was deemed to flow from positive to negative and that has stuck to a greater extent ... its called Conventional Current flow

current IS really the flow of electrons from negative to positive

In the case of a battery supply, as you have shown, the chemical action in the battery separates the charges to produce positively charged Ions ( atoms with too few electrons for their atomic number) to accumulate at the positive terminal, and for electrons to accumulate at negative terminal

Contrary to popular belief, a battery doesn't store energy as such. The overall charge in a battery is Zero
When a battery is Flat .... that is, cannot supply a current any more ( has little or no potential difference between the terminals) its not because the battery has run out of charge ( electrons) Rather it is that the chemical reaction in the battery has stopped and it can no longer separate the + and - charges

more to come.....

 

[davenn]

So would current flow from the top (+) into the resistor (Which will control the amount of current to flow into the LED then back into the (-)? Or would it be vice-versa? if thats the case then shouldn't the Resistor be before the LED if the current flows from the (-) of the battery?

it doesn't matter where the resistor is placed it still has the effect of limiting the current flowing in the circuit in circuit drawings, it is conventional to show it in the positive lead as shown in your pic

I understand the life of atoms and electron, etc. Just a bit confused as to how the electric current actually flows?

Take your circuit above, connecting wires, resistor and LED .... in those 3 parts together, there are a fixed number of electrons
for every electron that comes out of the battery negative terminal into the circuit, one electrons leaves the circuit and goes into the positive terminal to combine with an ion and produce a neutral atom

The flow of electrons in a circuit is very slow a few mm / second ( varies with current flowing) google electron drift
The ampere is a measure of the amount of electric charge passing a point in an electric circuit per unit time, with 6.241×10¹⁸ electrons (or one Coulomb) per second constituting one amp 1 A = 1 Coulomb/sec

I have had bigger schematic, that contain both VCC and negative VCC, etc. They get more elaborate and crazy, so all i want to know is how does current flow? it helps me visually label what component the flow of current will hit first, or estimate the first contact!

in a dual rail supply, the current is splitting into both sections

hopefully I have answered all questions
come back with more if you haven't quite understood

cheers
Dave

 

[AndreeU17]

before it was known that electrons existed and that they were the charge carrier
Current was deemed to flow from positive to negative and that has stuck to a greater extent ... its called Conventional Current flow

current IS really the flow of electrons from negative to positive

In the case of a battery supply, as you have shown, the chemical action in the battery separates the charges to produce positively charged Ions ( atoms with too few electrons for their atomic number) to accumulate at the positive terminal, and for electrons to accumulate at negative terminal

Contrary to popular belief, a battery doesn't store energy as such. The overall charge in a battery is Zero
When a battery is Flat .... that is, cannot supply a current any more ( has little or no potential difference between the terminals) its not because the battery has run out of charge ( electrons) Rather it is that the chemical reaction in the battery has stopped and it can no longer separate the + and - charges

more to come.....

So from my understanding, that its convenient to view the flow of current from positive to negative but in the written description, the actual flow of current is from (- charge) electrons to (+ charge) protons. I wasn't really sure what you meant in the bottom, got a bit confused in the last paragraph about the battery been flat. When you mean flat, are you referring to the battery having not enough voltage to use (since its a battery). Or were you referring to the schematic symbol of a battery?

You say that the order of the resistor and LED wouldn't matter such since the resistor will control the current regardless of its location, however, dont LED need a resistor to prevent the LED from short circuiting ?

 

[Gryd3]

I gotta post a link.
http://www.allaboutcircuits.com/vol_1/chpt_1/7.html

This confused me for a while too... Many people refer to current flow in the 'Conventional' sense, and not the Electron Flow sense.

 

[davenn]

the actual flow of current is from (- charge) electrons to (+ charge) protons.

read what I wrote. to positively charged Ions ( atoms with a few electrons missing)

 

[davenn]

Take the conductive metal copper .... it has 29 protons and 29 electrons but only 1 electron is freely able to move between atoms

so when you look at a current of 1 A flowing 6.241×10¹⁸ you can see there are a lot of copper atoms in a small bit of wire

 

[AndreeU17]

Take the conductive metal copper .... it has 29 protons and 29 electrons but only 1 electron is freely able to move between atoms

so when you look at a current of 1 A flowing 6.241×10¹⁸ you can see there are a lot of copper atoms in a small bit of wire

Apperantly both forms of current flow notation are adequate for use. But would you suggest to use the actual proper Current flow notation over the conventional current flow? I feel like in the human eyes, its more conventional to see current flow from the positive surplus into the negative side rather than vice-versa. But since i'm taking this into account that i will be making my life revolve around electrical engineering, what is the best approach to use? Should i go for the obvious flow, or actually learn the real way current flows?

 

[davenn]

Apperantly both forms of current flow notation are adequate for use. But would you suggest to use the actual proper Current flow notation over the conventional current flow?

for everyday use, conventional is OK
when getting down to the details on what is really happening its better to use electron flow
Just don't use both in the same description of a circuit else confusion will incur

for me I always consider electron flow

Dave

 

[KrisBlueNZ]

Apperantly both forms of current flow notation are adequate for use. But would you suggest to use the actual proper Current flow notation over the conventional current flow? I feel like in the human eyes, its more conventional to see current flow from the positive surplus into the negative side rather than vice-versa.

I agree. I use conventional current except if I'm talking about the actual flow of electrons. That's relevant if you're talking about the internal operation of semiconductors, with their P and N materials and so on, where chemistry and physics are involved.

For general use when explaining how circuits work, I use conventional current, because conventional current flows in the direction of the arrow in circuit symbols such as diodes and transistors, and I find it more natural to think of current "coming into" the circuit from the positive rail (which should be drawn across the top of the schematic) and leaving via the negative or 0V rail (which should be drawn across the bottom of the schematic). In between the two rails, electrons (Edit: NOT electrons; I should have said "charges" or "current") follow gravity and move from the higher potential to the lower potential.

But since i'm taking this into account that i will be making my life revolve around electrical engineering, what is the best approach to use? Should i go for the obvious flow, or actually learn the real way current flows?

You know both ways. They're called conventional current flow and electron flow. If you're describing a circuit from a physics point of view, you should probably use electron flow. If you're describing it from an electronics point of view, I think it's better to use conventional current. Strictly speaking, conventional current is "wrong" because current is the flow of electrons, but if you think of it as the flow of holes, not electrons, it's right. It's just easier to understand because it fits with the schematic symbols and the normal way schematics are drawn.

If there's ever any doubt as to which one you should use, choose the one you think is most appropriate, and state which one you chose.

 

[Bluejets]

Just when you get your head around the above, then there comes transistors and movement of "holes" theory in which they appear to move but actually do not.
It's just a space where an electron used to be.
To be honest, I just remembered what the bloke said when he gave us the lessons, copied it into a part of my brain for entry into exam papers, and forgot about it after that.

 

[LvW]

Just when you get your head around the above, then there comes transistors and movement of "holes" theory in which they appear to move but actually do not.
.

Yes - and to complicate things: Nearly the same applies to electrons too. What we call "current" is NOT "flow of electrons" (they move very slowly!) but movement of charges (not charged carriers). But that`s pure physiscs and does not have any influence on designing/analysing circuits based on conventions.

 

[Arouse1973]

Umm I might upset people if I commented on this. So all I will say is Ben Franklin got it wrong, he had a 50/50 chance to get it right. We are now stuck with it as all the circuit diagram symbols lend them to conventional current. Most of the text books get it wrong so dont worry if your confused most people are.
Adam

 

[davenn]

You say that the order of the resistor and LED wouldn't matter such since the resistor will control the current regardless of its location, however, dont LED need a resistor to prevent the LED from short circuiting ?

Hi AndreeU17
just noticed this Q from you at the end of one of your posts ( hope you are still around and reading )

yes it does, no one said it didn't
the resistor will limit the current flowing in that series circuit it doesn't matter where it is

have a look at this diagram



I originally did this circuit to teach some Ohms Law about voltage drops across series resistors
But to work that out, you need to work out and realise that the current flow in the circuit is the same anywhere in the circuit .... across the top, the bottom, at points A, B, C and D

for the sake of discussion (ignoring the 1A marked) .... we could replace the resistor in the middle with a LED. And then have the combined values of the upper and lower resistors that equate to a single resistor value that allows for the correct current through the LED

cheers
Dave