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

[Entanglement]

how can I prove that no current would flow in a wire connected between two wires of equal potential. For an example a resistor of 2 ohms carrying a current of 3 Amp and a resistor of 3 ohms carrying a current of 2 Amp, and a wire "A" is connected between them. Obviously, the potential difference between the two wires is 6-6=0 but what is the explanation for the fact that no current will flow in Wire "A" I know that only as a fact but I can find an obvious clear explanation.

 

[Alpharup]

Kirchoff's current law is violated

 

[Alpharup]

Hey also, ypu are talking about potential difference and not potential.

 

[Entanglement]

Kirchoff's current law is violated

Please could you explain it in detail

 

[Crazymechanic]

if you connect something , like a wire between two points, wires whatever which both have the same potential then no current flows because they both are at the same level of voltage.

Just like water needs a slope or a decrease in height above sea level to flow.If you would have just a perfectly flat piece of land no rivers could flow.

 

[Entanglement]

if you connect something , like a wire between two points, wires whatever which both have the same potential then no current flows because they both are at the same level of voltage.
Just like water needs a slope or a decrease in height above sea level to flow.If you would have just a perfectly flat piece of land no rivers could flow.

Can you explain what is meant by the game the same potential ?

 

[Entanglement]

Have **

 

[Crazymechanic]

well a potential forms when there is some excess of charge (like positive or negative) if both are the same then there is no potential the material or whatever we say is neutral.
So if you have more positive charge on one side of the battery and more negative on the other or just ground in other cases ,then we say we have a potential difference and that can do work because the charges which are more at one point want to flow to the other point to equal out , while they flow , we say energy is being transferred and work can be done using that energy.

voltage or volts is just a measurement unit in which we measure the potential difference.

 

[Entanglement]

well a potential forms when there is some excess of charge (like positive or negative) if both are the same then there is no potential the material or whatever we say is neutral.
So if you have more positive charge on one side of the battery and more negative on the other or just ground in other cases ,then we say we have a potential difference and that can do work because the charges which are more at one point want to flow to the other point to equal out , while they flow , we say energy is being transferred and work can be done using that energy.

voltage or volts is just a measurement unit in which we measure the potential difference.

I got the part that electrons flow from high charge to low one
But a wire of resistance 3 ohms carrying a current of intensity 2 Amperes connected to another wire of resistance 2 ohms carrying a current of 3 amperes No current will flow between them although their intensities are different and quantity of electricity is different so there should be tendency for electrons to flow from high charge to low charge

 

[Crazymechanic]

well there is no high charge or low charge , charge is charge , there is more charge per given area or less charge per given are or no charge at all which means that the material is neutral it has an equal number of + and - charges in it.

about the resistors you mentioned remember that current or amperage is just another word like volts and voltage.the word itself means nothing you have to understand the meaning behind the word.

amperage or amps is the measure of how much charge flows in a given place at a given amount of time (1 second)
so you take a place in a wire and place an ampmeter in series with that wire , now close whatever circit you have there and see how many amps flows (charge flow) through that wire.
BUT if you have two wires and both wires are at the same potential ! this is the important part , then no current flows , yes it is correct that a resistor with less resistance will have a higher current , that is correct but a resistor can only have a current through it if it is either in a circuit (part of a circuit) or if it is in series with a wire which has a potential difference across it , like putting that resistor across the battery terminals you were talking earlier.
if there is no circuit and no potential difference no amps( charge) will flow through the resistor so you can connect it as you wish nothing will happen.

 

[Entanglement]

I mean that the amount of charge at A is more that at B, Although no current will flow through R?

 

[mfb]

I got the part that electrons flow from high charge to low one
But a wire of resistance 3 ohms carrying a current of intensity 2 Amperes connected to another wire of resistance 2 ohms carrying a current of 3 amperes No current will flow between them although their intensities are different and quantity of electricity is different so there should be tendency for electrons to flow from high charge to low charge

This is not a clear description of a circuit, and without additional information about the circuit it is impossible to tell if there will be a current flow.
If you connect two resistors in parallel, then different currents can flow through them. That should not be surprising.

Edit: I wrote my post before I saw your last post.

I mean that the amount of charge at A is more that at B, Although no current will flow through R?

A and B cannot be open ends, the current will flow to something else, so no charge is accumulating anywhere. Current is "charge per time" - and everything that flows in always flows out again (to a very good approximation).

 

[Entanglement]

This is not a clear description of a circuit, and without additional information about the circuit it is impossible to tell if there will be a current flow.
If you connect two resistors in parallel, then different currents can flow through them. That should not be surprising.

Edit: I wrote my post before I saw your last post.
A and B cannot be open ends, the current will flow to something else, so no charge is accumulating anywhere.

Check the figure that I posted before your post

 

[mfb]

You posted while I was already writing my post. See my edit in post 12.

 

[Entanglement]

You posted while I was already writing my post. See my edit in post 12.

I don't understand what do you mean? I just want to know if there is going to be a current through R or not considering that the amount of charge at A is more than That at B

 

[mfb]

I don't understand what do you mean?

I changed my previous post (you can change posts after you posted them, see the "edit" button in your posts).

I just want to know if there is going to be a current through R

That depends on the remaining circuit, especially the connections at A and B.

or not considering that the amount of charge at A is more than That at B

There are no charges hanging around, neither at A nor at B.

 

[xAxis]

I think what you say is "obvious" is the answer to a question. I doubt the question was "prove that no current would flow in a wire connected between two wires of equal potential". That's obvious.

 

[Entanglement]

thats the rest of the circuit

 

[mfb]

Okay. The 4Ohm-resistor has 3A as well (so it is between a voltage of 12V), and the 6Ohm-resistor has 2A (so it is between a voltage of 12V -> matches). As you can see, all electrons that come through the upper left resistor can go through the upper right resistor, and the same happens at the lower side. There is no current in the vertical line.

If you change one of the resistors, this changes.

 

[Entanglement]

Okay. The 4Ohm-resistor has 3A as well (so it is between a voltage of 12V), and the 6Ohm-resistor has 2A (so it is between a voltage of 12V -> matches). As you can see, all electrons that come through the upper left resistor can go through the upper right resistor, and the same happens at the lower side. There is no current in the vertical line.

If you change one of the resistors, this changes.

I have begun to really understand, but you are saying that the amount of charge at A is equal to that at B, then how are the intensities different ?

 

[Crazymechanic]

put two water reservoirs fill them with the exact same amount of water each, put a 1cm diameter hole at the base of one of them and put a 2cm hole at the base of the other what happens?

remember same amount of water in both reservoirs.

 

[mfb]

I have begun to really understand, but you are saying that the amount of charge at A is equal to that at B, then how are the intensities different ?

There is no amount of charge.
Forget that concept. It is wrong and it will just lead to confusion.

 

[Entanglement]

put two water reservoirs fill them with the exact same amount of water each, put a 1cm diameter hole at the base of one of them and put a 2cm hole at the base of the other what happens?

remember same amount of water in both reservoirs.

Water passes through both holes at same velocity but at different volumes proportional to both areas, what's your point?

 

[Entanglement]

There is no amount of charge.

Forget that concept. It is wrong and it will just lead to confusion.

Then what is the correct concept ?

 

[Crazymechanic]

the point is a resistor " RESISTS" to the flow of current just like thinner pipe resists to water flow, don't take this analogy for God as it is not perfect but it can make you understand better if you think a moment.

a given potential difference has a given amount of force it can exert on the current which is the flow of charge , the higher the value of the resistor the more that part of circuit resists that flow of charge , so you get more heat in the resistor and less current after the resistor.

have you ever played in garden with a water hose ? squeeze the end of it and it is harder for water to come out in the same quantity and usually it doesn't because it can't as it only has a given pressure.open the hose and you get more water flow as it is easier now for the water to flow out of the hose but as I said water is not electricity , and if you will get deeper with time into this you will have to use and understand what electricity is and what it does in different conductors, resistors, circuits etc.
But for the most basic idea of resistance and Potential you can use this one.
That's all.

 

[mfb]

Then what is the correct concept ?

Potential differences and currents. Nothing else is relevant in all circuits you'll ever see.

Currents are always balanced for all parts of the network - there is the same amount of current going in as there is current going out. If there are 2A coming from the left and 2A going to the right then there cannot be any current coming from above (with the geometry of your circuit).

 

[Entanglement]

Potential differences and currents. Nothing else is relevant in all circuits you'll ever see.
Currents are always balanced for all parts of the network - there is the same amount of current going in as there is current going out. If there are 2A coming from the left and 2A going to the right then there cannot be any current coming from above (with the geometry of your circuit).

Let's say that 5 coulombs enter the circuit 3 coulombs go through the 2 ohm resistor and 2 coulombs go throng the 3 ohm resistor but of course both of them would flow at the same velocity to keep the current flowing at the same pace through the whole circuit but doesn't that make point A more negatively charged then B which should create a potential difference between both points

 

[mfb]

As I said, those concepts are not useful, so please stop trying to use them. They will just lead to more confusion.

Each second, 5 Coulombs go through the whole circuit. 3 Coulomb per second go through the upper left resistor (towards A) and through the upper right resistor (away from A). There is nothing "left" at A. No charge that could accumulate there, the same amount flows in and out.

 

[Crazymechanic]

ok let's pause for a while.
when speaking of electricity the speed of current flow is meaningless , well I don't want to explain that now because it will ge this discussion into a chaos but all you need to know as mfb said is current (increase /decrease ) and voltage (potential difference) if you know them you can use them to understand and later calculate how much voltage drops on each resistors and other things.

 

[Entanglement]

As I said, those concepts are not useful, so please stop trying to use them. They will just lead to more confusion.

Each second, 5 Coulombs go through the whole circuit. 3 Coulomb per second go through the upper left resistor (towards A) and through the upper right resistor (away from A). There is nothing "left" at A. No charge that could accumulate there, the same amount flows in and out.

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

 

[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 dissappear 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.