Can Zero Electric Potential Prove No Current Flow in a Connected Wire?

[Crazymechanic]

NO NO NO ,

there is no slower faster current etc , in a classical way we can assume current as instantaneous because of the speed of electric field (which is c in vacuum and close to that in everyday circuit traces)

about the wires , it doesn't matter as long as both of them are set to the same potential , say 12 volts for example , all that happens is that the one with less resistance let's more current through and the one with higher resistance let's less current through.
Physically one resistor heats up more the other one less , there is nothing more happening here.
No negative potentials form anywhere no nothing forget that.

 

[mfb]

Yeah, but a wire of 3A and a wire of 2A wouldn't the 3A wire be more negative creating a potential difference I know that there is no accumulation in the wire as there is a repulsion force between the electrons and as the current should have the same pace along the whole circuit but I mean that the FLOW would make it more negative

The amount of electrons in a cable has nothing to do with electric currents. It is completely independent of them.

More current just means more directed motion of those electrons.

 

[tfr000]

If you have 2 ohms carrying 3 amps, and 3 ohms carrying 2 amps, it is obvious from Ohm's law that the voltage driving the current in both cases is 6V. Connecting 6V to 6V will result in no current flow. Anything more than this is over-complicating the problem.

 

[Entanglement]

What makes the intensity greater in a branch than in another? Its velocity or the amount of electrons ? I mean do the electrons move faster than in the other branch or because the amount of electrons per unit area increase

 

[Crazymechanic]

Ok , now were getting somewhere , they don't move faster slower the field causes them to move so all you need to accept in movement is that whenever there is a PD and a closed circuit or path to ground, there is a net movement of those electrons in one or other direction which is called current , so there is current.

Now we concluded and I think you agree that current is quite simply speaking the amount of charge that passes a point in wire in a given amount of time.So if higher ohm resistor let's less current through then what is your conclusion what happens?
the resistor absorbs some of the charge and it is being transformed into heat.
put more resistance and even less current will go through , and so you can go up and up until for a given potential difference there will be no more current flow , the current will be blocked by the resistor.

this is how a potentiometer works , you know like the volume controller knob on your recorder or radio.

 

[Entanglement]

Ok , now were getting somewhere , they don't move faster slower the field causes them to move so all you need to accept in movement is that whenever there is a PD and a closed circuit or path to ground, there is a net movement of those electrons in one or other direction which is called current , so there is current.
Now we concluded and I think you agree that current is quite simply speaking the amount of charge that passes a point in wire in a given amount of time.So if higher ohm resistor let's less current through then what is your conclusion what happens?

the resistor absorbs some of the charge and it is being transformed into heat.

put more resistance and even less current will go through , and so you can go up and up until for a given potential difference there will be no more current flow , the current will be blocked by the resistor.
this is how a potentiometer works , you know like the volume controller knob on your recorder or radio.

So when an intensity in a branch is higher than in another it's just because there are more electrons per unit area but speed remains constant along the whole circuit

 

[sophiecentaur]

You are all, presumably, talking about DC. Any resistor will be production kTB of noise power, in a bandwidth B and a hotter resistor will be producing more electrical noise power than a cooler one. This means that there will be a net flow of electrical energy from the hot to the cold and a 'varying PD'. (if you care to look at it that way)

 

[mfb]

The electrons are moving faster if the current is larger (and if everything else is equal).
The density of electrons is always equal to the density of protons, so there is no net charge.

@sophiecentaur: I don't think it is helpful to add those complications as the question is really basic.

 

[Crazymechanic]

I must say sophie I'm not sure if the OP understood a single thing from what you just said , I'm not even sure about myself , will have to take a look about this.

 

[Entanglement]

The electrons are moving faster if the current is larger (and if everything else is equal).
The density of electrons is always equal to the density of protons, so there is no net charge.

@sophiecentaur: I don't think it is helpful to add those complications as the question is really basic.

But the speed of electrons in two parallel branches have to have the same speed even if their intensities are different isn't that right ?

 

[mfb]

No.
And I don't see any reason to expect that.

 

[Entanglement]

No.
And I don't see any reason to expect that.

You told me what goes in must go out at the same time then how could the speeds be different ?

 

[mfb]

You told me what goes in must go out at the same time then how could the speeds be different ?

If you have a big, fast-flowing river next to a small, slow one, both won't accumulate water, but the big river has a higher flow rate.

 

[Entanglement]

42 replies and I still can't understand it I'm so stupid

Mfb and crazymechanic I really appreciate your help

If you have a big, fast-flowing river next to a small, slow one, both won't accumulate water, but the big river has a higher flow rate.

I understand the no accumulation would happen I just can't understand why there isn't any potential difference between two wires with different intensities even if Potential is equal

 

[mfb]

"equal potential" and "no potential difference" are exactly the same.
5 and 5 are equal numbers, and the difference between them (5-5=0) is zero.

Please use the edit button, don't make multiple posts in a row.

 

[Crazymechanic]

you need to think in terms of total energy , if you have say 5 volts and 5 amps input and then you have two resistors in parallel which are in series with the input , one of the resistors is 3ohm the other 2ohm , now there will be more current through one of them because it will be easier for most of the current to get through that one , and there will be less current through the other because it will be harder for the current to get though the other , but the overall picture doesn't change you still have 5 volts and 5amps and they can't just disappear because of slower or faster flow , the flow probably mixed your mind , all you actually need to understand is that if you have two different resistors and one source of energy then that source will divide itself on each of the resistors respectively with their resistance but the end picture the overall situation doesn't change.

imagine a river , let's say that it has a certain amount of water flowing in it , there will be places were the river will get narrower and faster and there will be places were the river gets wider and slower but the overall amount of water hasn't changed.

http://physics.bu.edu/py106/notes/Circuits.html

read this one.

maybe the water analogy messed your mind a little , in circuits you don't need to look at the flow of charge (most cases electrons) you just need to understand that current flows , doesn't mater how fast , because there is a field which acts upon it and as I said it is almoust instantaneous, you just need to understand that there is current which is the flow of charge and then there is PD (voltage) which is related to current.
later when you will be familiar to all these things you will be able to look upon and understand why the speed of the actual current flow does't mean much here.

 

[Entanglement]

But if you have a river splitting into two branches one of them is narrow and the other is wide and then you made connection between them, certainly water will flow from the wide one to the narrow one

 

[Entanglement]

Hey guys thanks for your patience and dignity, you made the idea a lot closer I just need to read more about the electric field and electrons flow to understand more, thanks a lot !

 

[xAxis]

You can look at the problem like this. 3amp current flows where resistance is lower, so charges flow more freely. On the other wire the voltage is the same, so charges there tend to flow equally fast, but because resistance is bigger, they slow down and become more dense. So the net charge is equal.

 

[sophiecentaur]

The electrons are moving faster if the current is larger (and if everything else is equal).
The density of electrons is always equal to the density of protons, so there is no net charge.

@sophiecentaur: I don't think it is helpful to add those complications as the question is really basic.

My comment was tongue in cheek but not entirely. Along with a lot of threads on PF, people are using 'electrons' as if they knew what they are and how they are really behaving in a metal. (They clearly do not, in many cases.)
Which sub-set of our current knowledge of electrons is actually being used in these discussions? (To be fair to readers, it should be declared each time). I have to ask whether it really is helping in an 'understanding' of all this. People seem to think that using the word 'electron' makes everything somehow more weighty and learned. How many times do people actually realize that it is the mean velocity (drift velocity) that constitutes the current. What is being used here is largely a hydraulic model in thin disguise. What actually is wrong with just using the words Charge and Current? I really do question whether members who know a bit more about this are really helping those who want to learn by 'indulging' them in this over simplified model without using the caveats that should be used.
I have made this point this several times but, if this over simplified model was really a way forward, how come it is not used, either in circuit theory or in more advanced studies of conduction? It can't be because it's too hard to understand. I just think it should carry a serious health warning for people who are trying to learn more about all this.

 

[Crazymechanic]

But if you have a river splitting into two branches one of them is narrow and the other is wide and then you made connection between them, certainly water will flow from the wide one to the narrow one

This is what you said ,

this is a very important point , imagine a river spliting in half , say an island is seperating the river at some point , one side is narrow the other wide , you say that why doesn't water from the wide part flow back into the narrow part after the split , but think about it, if it could flow into the narrower part after the split then why didn't it flow there right in the beginning before the split ??

The answer is because it couldn't , it didn't have enough force or in our case PD to do that.
The narrower split takes more force to get the same amount of water through than the wide one.

if you have a given PD (volts) you can do only a given amount of work with them.
As current flows it is easier for the current to go through the least resistance and it does exactly so , and no mater before or after it doesn't flow back into the higher resistance just because it is HIGHER.

This is the point, if more current couldn't flow through the higher resistor before it, then why would it do that after it... :)

 

[sophiecentaur]

I must say sophie I'm not sure if the OP understood a single thing from what you just said , I'm not even sure about myself , will have to take a look about this.

That may well be true. But if you want to talk about conduction electrons then you have to talk about thermal electrons in the same model. My post above points out that this simple model of electrons is no better than a water analogy. Just calling the charge carriers electrons is no better than calling them Charge Carriers (unspecific and with simple electrical properties). Just because an explanation gives people an impression of understanding, it may not necessarily be helping them. There's recently been a massive thread about 'how the energy is carried' in which people have aired a range of views and personal explanations, many of them flawed and based pretty much entirely on this hand waving electron model. That thread demonstrates the very thing I am warning about.

 

[Crazymechanic]

I really do get your point and I got it before long ago when we talked about the same idea on a thread here.

I think this thread is pretty nice as the OP is constantly being pulled back to current and voltage and the basic parts of water and rivers that can be compared to current , and as I said if the OP will understand this and move forward he will be able to talk in more complicated terms and learn them because the simple water analogies will break down at that point but for now let's see what the OP thinks about the answers that have been given in the past minutes in this thread.

 

[Entanglement]

This is what you said ,

this is a very important point , imagine a river spliting in half , say an island is seperating the river at some point , one side is narrow the other wide , you say that why doesn't water from the wide part flow back into the narrow part after the split , but think about it, if it could flow into the narrower part after the split then why didn't it flow there right in the beginning before the split ??

The answer is because it couldn't , it didn't have enough force or in our case PD to do that.
The narrower split takes more force to get the same amount of water through than the wide one.

if you have a given PD (volts) you can do only a given amount of work with them.
As current flows it is easier for the current to go through the least resistance and it does exactly so , and no mater before or after it doesn't flow back into the higher resistance just because it is HIGHER.

This is the point, if more current couldn't flow through the higher resistor before it, then why would it do that after it... :)

cool nice analogy

 

[Entanglement]

cool nice analogy

I want to read a lot about electron flow behaviors at about circuit where can I find that ?

 

[Crazymechanic]

I think it would be great to read about current flow, voltage (PD) , look at simple circuits and how they work , trust me wanting to read stuff yu are not ready to understand will not make you understand it.
You need to build the house from the basement not from the roof.

 

[sophiecentaur]

I really do get your point and I got it before long ago when we talked about the same idea on a thread here.

I think this thread is pretty nice as the OP is constantly being pulled back to current and voltage and the basic parts of water and rivers that can be compared to current , and as I said if the OP will understand this and move forward he will be able to talk in more complicated terms and learn them because the simple water analogies will break down at that point but for now let's see what the OP thinks about the answers that have been given in the past minutes in this thread.

In the light of the comment by Elmorshedy, below, I wonder how you now feel about things.

I want to read a lot about electron flow behaviors at about circuit where can I find that ?

I would say that you are unlikely to find very much at all. Electron flow within devices is studied, of course, but, as Crazymechanic and I (and others have written), it is current that is the relevant quantity in "circuits". Have you not gathered that from the past few dozen posts?

Would you expect to find a book about Quantum Physics in the design of Steel Bridges? This is, effectively the sort of thing you seem to be after. Scientific knowledge is appreciated in 'shells', for a very good reason. It's hard enough to deal with it when it's split into levels. Why do you think it would be easier to condense the levels all together.

 

[Crazymechanic]

In the light of the comment by Elmorshedy, below, I wonder how you now feel about things.

Yes Sophie , I see that he wants to dwell into electrons.I think this is not only the fault of some teacher/s or the electron model , I think this is just the thing we all kinda had in our childhood when we wanted to max out on everything we could get our hands on , the feel that you need to understand everything with one blink of an eye.
I assume from the OP's language he is still pretty young , in his teens probably , so that would explain this tendency, those who really feel fanatic and willing to learn catch later on , I mean the truth is out there , those who truly seek will find it anyway , but better if they listen to the advice they are given.

 

[Entanglement]

Yes Sophie , I see that he wants to dwell into electrons.I think this is not only the fault of some teacher/s or the electron model , I think this is just the thing we all kinda had in our childhood when we wanted to max out on everything we could get our hands on , the feel that you need to understand everything with one blink of an eye.
I assume from the OP's language he is still pretty young , in his teens probably , so that would explain this tendency, those who really feel fanatic and willing to learn catch later on , I mean the truth is out there , those who truly seek will find it anyway , but better if they listen to the advice they are given.

All experts were beginners one day

 

[sophiecentaur]

All experts were beginners one day

True. As only a mild sort of expert I can say that we were not taught 'the electron way' because our teachers were too sensible to let us think that 'electrons' were understandable enough to be the 'explanation' for anything we were likely to come across until University.
That approach has proved extremely useful in later life because I have never risked using a trivial model when trying to grasp difficult things.

[edit: This is especially true if one demands a non-mathematical, "Physical" explanation.]