Makes you realize the huge number of free electrons contained in a conductor. One ampere is one coulomb per second or 6.241 × E18 electrons per second. So since three amperes for one hour moves 6.74 x E22 electrons 1 meter, then 1 meter of a 1mm wire contains that number of free electrons................................
The Wikipedia entry for electron drift velocity shows an example calculation of a 3amp current flowing through a 1mm wire results in the electrons taking 1hour to traverse a distance of 1 meter. A surprisingly large bulk of electronic hobbyists don't realize this.
so this means the sum of Voltage of LED1 and LED2 = The Voltage output recorded from the 'output' of the potentiometer ?The sum of the drops equals the source voltage.
DerStrom8,
That is all correct as far as the external current goes. But, the +ions that give up their electron for external current have to go to the cathode where they receive a returning electron and get neutralized. That path is within the battery, and is an example of a positive charge moving. This has to happen, otherwise the anode would clog up with +ions and the cathode would clog up with electrons. Therefore an internal current of positive charges exists within the battery to neutralize the internal charge build up. This positive charge internal current has to equal the external negative charge current.
Ratch
The way I measure the Voltage is to connect each probe to the LED leg. For LED 1 & LED 2 I'm getting the same reading (for Voltage) which is exactly what the theory says that 'serial resistors will read the same Voltage'. I'm also getting the same reading for Current which is correct ?.
The +ions, after giving up an electron, do not move much within the battery.
The current flow we really care about is on the outside, not the inside.
Conventional current flow is said to go from the cathode, through the circuit, and back into the anode, which is just plain wrong.
The current (defined as the flow of electrons) exits the anode, flows through the circuit, and moves back to the cathode. There is no way to argue that--it is a fact.
DerStrom8,
I beg to differ. See https://www.explainthatstuff.com/batteries.html under the paragraph "Chemical Reactions". We are talking about a chemical battery, not a dynamo. In electrolysis, ions move.
Care or not, the internal current has to match the external current.
Not quite accurate. The conventional current/voltage (CCV) method mathematically assumes positive to negative charge movement of a voltage source. The CCV does not concern itself with the actual polarity or the physical direction of the charge carriers. It only give a calculated value from which the user can then deduce what the true direction of charge flow is.
Yes, that is what happens externally. No one denies that fact. But there is an internal current also, whether of interest or not.
Ratch
I don't think that's entirely correct. When the oxidizer atoms (parts of the + electrode material) give off electrons, they become ions, but they do not "move" towards the cathode. They are part of the cathode. Current is defined as the "Movement of electrons", which is what is really important.
One could be an electronic engineer his/her entire life and he/she would not need to know about the positive ions within a battery. The only thing that is really important to know in a circuit is what happens on the outside of the battery.
I am not arguing with you saying that conventional current flow can't be used in math. I'm saying it can't be assumed to be true in the physical world. Current does not flow from + to -. That's all I'm trying to say.
I agree, there is an internal current, but it is very small. It is negligible and does not really affect the operation of a battery when considering what's on the outside.
DerStrom8,
Obviously the anode material cannot be part of the ions traveling to the cathode. There won't be any material left on the anode before long if that happened. The link does not say that happens. No doubt, a secondary reaction in which the electrolyte gives up an electron to the anode, and then moves to the cathode to receive a replacement electron occurs. The point is that there if a current of positive ions within the battery.
Current is defined as the movement of charge carriers per unit of time. That includes the positive charge carriers, too.
Unless you are a battery engineer. That is becoming an important field of endeavor these days.
Not that CCV cares, but current does exist in the + to - if the charge carriers are positive. Not all electric circuits are through metallic wires, which are predominently negative charge carriers.
The internal battery current has to equal the external battery current OR Kirchoff's current law will be violated.
Ratch
Why do you think batteries die? It is because as the oxidizer gives off electrons, it decays. The remaining ions attract the electrons to the cathode, but the material still gives way a little bit. After a period of time, it will lose too much of its oxidizer to sustain current flow.
Ok, I'll give you that, but it does not change my main point.
Now you're just picking nits.
Sure, but in a simple series circuit with, say, a battery and a resistor (as I discussed earlier), the dominant, important charge carriers are electrons. I'm pretty sure I went over this before....
Yes, but the important internal battery current is the electrons flowing from the oxidizer to the anode. Not the "movement" of +ions.
DerStrom8,
I did not know we were talking about dying batteries.
Which was?
Well, you cannot aver that one particular aspect of EE like circuit analysis is more important or should deserve more attention than another less interesting branch of electronics.
As did I. In a equally simply circuit, a battery in series with another resistor, a slab of PNP semiconductor material will have positive holes as the predominant charge carriers.
As I stated before, a battery is a chemical entity, not a dynamo. Ions have to be created and move in order for it to work. Also they have to balance with the external flow of electrons they cause. If electrons flowed within the battery, then no ions would need to exist. But since there are no magnetic fields with a battery like there is in a dynamo to move the electrons along, that cannot happen.
Ratch
Come on Ratch. I'm sure you know as well as I do that ALL batteries in the real world die after a certain amount of use!
That the carriers and current flow we really care about is the flow of ELECTRONS in a simple series circuit. How many times do I need to repeat that?
My point has nothing to do with types of electrical engineering. My point was that the "movement" of +ions is negligible and is, in fact, unimportant in most cases.
.
I'm not talking about "slabs of PNP semiconductors"! I'm talking about a basic series circuit with only a battery and a resistor. I'm not talking about semiconductors here!
Ions are not just "created". The electrons are stripped, and pushed/pulled around the circuit, which is current flow.
When the electrons are taken from the oxidizer, it leaves positively charged ions at the cathode, which attract (pull in) electrons. However, in order for the electrons to get back to the cathode, they must go through the circuit first. That's how batteries work. Period.
The only "flow" of +ions is a tiny amount of movement within the battery, when the electrons coming to the cathode get close enough to pull them (as they are pulling the electrons).
The positive ions DO NOT move around the circuit--only slightly within the battery.
DerStrom8,
Certainly that is true. I just did not know that we were discussing dead and dying batteries.
Well, "we" does not include me. I am interested in all aspects charge carrier movement.
And my point is that the ion current has to equal the external electron movement, and cannot be ignored if proper understanding is needed.
And does not a slab of PNP semiconductor have resistance?
I assume you are referring to the external flow. Except for the "current flow" phrase, I can agree with that.
When electrons are taken from the electrolyte in the vicinity of the anode, which supplies electrons to the external circuit, ions are created and travel internally through the battery to the cathode where they pick up a returning electron and become neutralized.
For every electron that travels the external circuit, a positive ion has to make the trip from the anode to the cathode within the battery. Otherwise the charges would accumulate, which does not happen.
Only electrons move external to the battery. But the +ion current has to match the external electron current. The electrons cannot move within the internal battery because there is nothing to propel them like there is in a dynamo. They have to go through the chemical ion neutralization process to get back to the anode.
Ratch
MrAl said:For your example (which was a good one BTW) we have few hobbyists who know how fast charges travel down a wire. But we have zero hobbyists who need to use this information for any practical project they are building
Jon Wilder said:Quite honestly I'm not sure why anyone even cares about the chemical reaction and the activity which happens in a battery. Unless you are a battery engineer it's not something you really need to know. Just know that externally, electrons flow from the negative terminal, through the external path which exists between the battery's terminals, and returns back to the positive terminal until the charge difference that exists between the terminals is depleted.
Jon... If you look at a battery from that standpoint you'd be like every engineer that ever made a cordless phone that uses a NiMH battery that is trickle charged constantly on it's base which causes them to fail after 1 year of use because the chemistry is destroyed from the subtle overcharge, a properly designed NiMH charger would let the battery last 5+ years.
It is paramount to someone using electronics that uses a battery to know how they work. Nowdays you can get some pretty sophisticated charge controllers which take the need for this knowledge away, but if you don't know in the first place why you need to use a charge controller because you don't know anything about batteries then you will be a horrible engineer!
You know why those charge controllers are being used? Because soem electrical engineer that don't know anything about battery chemistry improperly used Lithium Ion batteries which were caused to explode or burst into flames because they didn't know anything about battery chemistry proper utilization and charge control methods!
Too much in teaching I see 'black boxing' of ideas and concepts like this, and it results in crappy products to end users because the education system has failed to see that there is no way to dumb down this stuff, you gotta know a lot to do ANYTHING well.
...However, it is not the ion "flow" that does the work--it is the electron flow through the circuit.
...I'm talking about a basic resistor, NOT a "slab of PNP semiconductor"!
Woah, electrons are NOT taken from the electrolyte. The electrolyte is what strips the electrons from the oxidizer. Once stripped, the electrons flow through the electrolyte to the anode, and out the terminal. Then they flow around the circuit, back into the cathode, and "meet back up" with the ions. Other than the part about electrons being taken from the electrolyte, I agree with that quote.
That is why, for this thread, I have been discussing electrons--THEY are what are important in this case, NOT the ions.
And it is the movement of electrons OUTSIDE of the circuit that is important.
Hi all,
The discussion is interesting but it's beyond me at this stage I know that battery is power sourcethe discussion is really confusing me. It would be easier for me to follow the thread if we can discuss about the circuit that I've setup in the breadboard with the picture that I've posted so I can follow the discussion again
Thank you for your help.
Cheers
DerStrom8,
Yes, but if the ion flow stops, so does the external electron flow.
It is still a resistance. Not a commercial resistor, but still a resistance.
I am calling the oxidizer, stabilizers, fillers, and anything else between the cathode and anode an electrolyte.
I guess we are going to have to disagree about whether the electrolyte gives electrons to the anode and takes them back from the cathode. And whether electrons travel internally through the electrolyte instead of ion generation and ion neutralization occurring.
And if the electrons cannot move outside of the battery without ions moving inside the battery, then the ions are just as important.
Yes, that is a point I had long forgotten.ljcox,
No, because then it would have units of joules (MKS) instead of joules/coulomb. Voltage is a density, not a unit of electrical potential energy.
See below.
Because of its potential energy, measured in joules (MKS).
Qualitatively yes, but a quantitive definition requires a per unit of time also.
Yes, I = dq/dt but that makes it a bit complicated for beginners.
Mathematically assumed to be positive to negative charge movement of a voltage source.
Movement of a voltage source???
Ratch
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?