Since when is the flow of electrons not the flow of electrical charge (where 1 electron has a charge of ≅ -1.60217657 × 10E-19 coulombs)?
And the flow is indeed measured in amperes (coulombs per second).

Particularly since the advent of semiconductors - current flow is sometimes expressed in terms of the movement of holes.

The movement of holes is in the same direction of the notional direction of conventional current.

 

At last someone has acknowledged my post#18

Which merely acknowledged my Post #3.

 

I use conventional current and I measure current in amperes.

Any problems?

I didn't make myself clear. I was still trying to illicit an answer to my question in Post #52 which is, "If you want to use electron flow and measure current as being positive in the direction of electron flow, what units do you use for that current since it is NOT amperes?"

 

Of course there's a difference. Not necessary to be patronizing.

But you previously stated that
"In the second case you are using current as being the flow of electrons and NOT the flow of electrical charge. What are the units of current in this case? It is NOT amperes."
I don't understand how you can make that statement based upon the sign of the charges. Either way the charge flow is in amperes. The conventional current flow is from plus to minus, the electron flow is minus to plus.

So you ARE saying that when the electrons are flowing from A to B that the flow from A to B, using the electron flow convention, is +1C/s and that, somehow, by having a positive flow of charge going from A to B that B ends up negatively charged. Just where does this magical mystery minus sign come from?

 

So you ARE saying that when the electrons are flowing from A to B that the flow from A to B, using the electron flow convention, is +1C/s and that, somehow, by having a positive flow of charge going from A to B that B ends up negatively charged. Just where does this magical mystery minus sign come from?

So, in a vacuum tube; the voltage applied to A will conduct an Electromagnetic wave which extends to B thus exciting B then once excited will in turn supply the necessary - voltage needed to create current flow from + to -

Like in a lightning strike from cloud to cloud or am I missing everything. lol

Thanks in advance.

kv

 

I didn't make myself clear. I was still trying to illicit an answer to my question in Post #52 which is, "If you want to use electron flow and measure current as being positive in the direction of electron flow, what units do you use for that current since it is NOT amperes?"

Current is measured in amperes, as Wikipedia puts it "The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second."

Note that is the unit. The scaler quantity is a different question entirely.

 

Current is measured in amperes, as Wikipedia puts it "The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second."

Note that is the unit. The scaler quantity is a different question entirely.

Yes. That is the unit for electric current. But electrons/second is not the flow of electric charge, it is the flow of charge carriers, each of which has a particular electric charge that has to be taken into account.

Imagine an ion beam consisting of helium nuclei, such as from the Am-241 source in a smoke detector. For simplicity, let's say that we have a really, really, hot source and there are 6.24E18 nuclei traveling from the source to the target each second. What is the electrical current from the source to the target. It is not 1A. To get the electrical current you need to do the math:

I = [6.24E18 (He^2+)/second][(2)(1.602E-19C)/(HE^2++)][1A/(1 C/s)] = 2A

The exact same approach would be used if you had charge carriers that had three excess electrons each on a molecule X

I = [6.24E18 (X^3-)/second][(3)(-1.602E-19C)/(X^3--)][1A/(1 C/s)] = -3A

And the exact same approach would be used if you had charge carriers that had one electron worth of charge, say an electron.

I = [6.24E18 e^-/second][(1)(-1.602E-19C)/(e^-)][1A/(1 C/s)] = -1A

 

Current is measured in amperes, as Wikipedia puts it "The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second."

Note that is the unit. The scaler quantity is a different question entirely.

Note the article you cited on the coulomb:

"It is equal in magnitude (absolute value) to the charge of approximately 6.241×1018 electrons, but has the opposite sign."

Also note just below that where they provide the SI definition: "the charge transported by a constant current of one ampere in one second."

\(
1 \;C \; = \; 1 \; A \; \cdot \; 1 \; s
\)

So if you have a stream of charged particles traveling to an object and that object's charge goes from 0C to -1C in one second, by definition the current that flowed to that object during that time is -1A.

Note that no where in here is any assumption of conventional flow or electron flow. Whatever convention you want to use has to be consistent with this definition of charge and current.

If someone really wants to say that the current is 1 ampere, then they have to do one of two things, neither of which the electron flow crowd does: You either have to declare electrons to have positive charge and then multiply all of the voltages in the system by -1 or you have to change all of the formula so that, for instance, you use:

\(
1 \;C \; = \; -1 \; A \; \cdot \; 1 \; s
\)

Otherwise your system is inherently inconsistent and requires you to perform magical mystery negations here and there in order to get correct answers.

 

Yes. That is the unit for electric current. But electrons/second is not the flow of electric charge, it is the flow of charge carriers, each of which has a particular electric charge that has to be taken into account.

Imagine an ion beam consisting of helium nuclei, such as from the Am-241 source in a smoke detector. For simplicity, let's say that we have a really, really, hot source and there are 6.24E18 nuclei traveling from the source to the target each second. What is the electrical current from the source to the target. It is not 1A. To get the electrical current you need to do the math:

I = [6.24E18 (He^2+)/second][(2)(1.602E-19C)/(HE^2++)][1A/(1 C/s)] = 2A

The exact same approach would be used if you had charge carriers that had three excess electrons each on a molecule X

I = [6.24E18 (X^3-)/second][(3)(-1.602E-19C)/(X^3--)][1A/(1 C/s)] = -3A

And the exact same approach would be used if you had charge carriers that had one electron worth of charge, say an electron.

I = [6.24E18 e^-/second][(1)(-1.602E-19C)/(e^-)][1A/(1 C/s)] = -1A

I have no idea what point your calculations are intending to prove, though I do note in all cases the result is in the units of Amps.

I do get the impression you are a bit foggy on the definition of "unit".

 

WBahn
Which merely acknowledged my Post #3.

That is because it was intended to reinforce your post, which I felt was unclear and did not properly bring out the fact that there are two separate sign conventions involved which is where most of the confusion comes from since people are usually only thinking of one.

for every directed quantity one employs one needs a sign convention.
Vectors are always directed quantities, but directed quantities can be other things (sometimes simpler) as well as vectors.

With respect I think this is the basis of your dispute with ernie and others and the resolution is for all to recognise the separate sign conventions that are used for the separate quantities involved.

 

I have no problem if someone wants to use another sign convention, I just wish they would use it consistently -- which they don't.

If they want to claim

1A = -1C/s

Then okay, but they don't. They want to pretend that they are still using it to be 1C/s and try to get around this by applying magical mystery negations here and there. If they were being consistent there would be absolutely no need for this.

The want to use the normal relationships such as i=dq/dt but, again, their convention is not consistent with this.

 

I have no idea what point your calculations are intending to prove, though I do note in all cases the result is in the units of Amps.

I do get the impression you are a bit foggy on the definition of "unit".

The point is that, in all cases, if you want to use amperes then the result must be for the flow of CHARGE, not for the flow of CHARGE CARRIERS.

I most definitely do understand the definition of a unit.

Just answer some simple questions from the point of view of someone that wants to use electron current.

Which of the following is correct:

1) The amount of charge Q that passes a point when a constant current I flows for a time T is:
a) Q = I·T
b) Q = -I·T

2) What is the current flowing from the negative terminal of a 12V battery to the positive terminal of a battery through a 1Ω resistor:
a) 12A
b) -12A

3) How much charge flows into the positive terminal each second in the battery in the question above:
a) 12C
b) -12C

 

You will have to find someone who uses electron flow to answer your quiz.

However I do note that in question 2 that all the answers have the units of Amperes.

 

1)WBahn
The amount of charge Q that passes a point when a constant current I flows for a time T is:
a) Q = I·T
b) Q = -I·T

Suppose some charge, Q is circulating around a point, P.

Then how much charge passes P per unit time?

 

When I went to the university to get my BSEE we were taught current flows from positive to negative and we did all of our calculations with this convention. The textbooks throughout our electrical engineering courses used this convention. And yet we were taught the truth: that current actually flows from negative to positive. Nevertheless, science persists in the conventional positive to negative direction. The calculations are based on this presupposition and they work no matter which way the current actually flows. Okay, so far so good. But then I run into electrical technician sources and they insist on thinking in terms of negative to positive such that the little arrows on the diode and transistor symbols are backwards. Why is this counter intuitive system of thinking gaining ground? I, for one, will never draw my KVL loops backwards, for that would involve the complication of most of the numbers being negative. I like to work with positive numbers. Any thoughts on this?

Hello,

I realize this is a long thread so i may have missed some posts but hopefully this helps a little anyway.

For most things we can use either convention and so we choose to use the conventional current flow (pos to neg) because we dont have to keep working with the sign and determining it's meaning. For example, E=I*R, where if we observe a negative current then we get a negative voltage like:
E=-1*2=-2 volts
but then we have to determine what that resulting sign means too. So it's easier to think of it in terms of positive quantities.
This all fits pretty neatly into the context of electronic circuits, but when we move into the context of physics, the sign sometimes becomes important. So in physics it is better to use electron current flow while in electronics it is simpler to use conventional flow.
Notice that the difference between Faraday and Lenz is only the sign, where it is included in Lenz's while it is absent in Faraday's.

 

You will have to find someone who uses electron flow to answer your quiz.

However I do note that in question 2 that all the answers have the units of Amperes.

So? I never said that if you define the symbolic current flow to be in the direction of electron flow that you couldn't express the current in amperes, merely that you couldn't use amperes if you insisted that such flow was positive.

If you would take the time to read what I have said several times, I said that if you want to use a positive value for the flow of current flow in the direction of electrons then you can't use amperes. I have said over and over and over that the value of current in the direction of electron flow is negative and I have given example after example.

 

It only now dawned on me that putting a charge on a capacitor requires pulling the electrons out of it. A Coulomb of charge is an absence of electrons. Never though of it that way until all this talk about sign conventions.

 

Suppose some charge, Q is circulating around a point, P.

Then how much charge passes P per unit time?

I take it that you can't answer those simple questions. Why are they so easy to answer for anyone that uses conventional current flow but I can't get anyone that uses electron flow to answer them. Could it be that people are realizing that they can't give the answers they would like to give without having to face the inconsistency in what they've been doing for years?

As for you question and attempt to derail the discussion, I don't know what the context is that you are talking about. I have a feeling that as soon as I answer that you are going to then ask about electrons "orbiting" a nucleus and how that contradicts what I say, ignoring the fact that one the quantum scale things often contradict the large-scale classical view.

Although I asked about a point P in my question, as that is the way such questions are typically stated, I have often qualified similar statements with something like, "or more accurately, through a particular area of interest". If the area of interest (which is assumed to include the point P) cuts both paths that the charge is travelling ("outbound" and "inbound"), then the net current through that area is zero. If you reduce the size of the area so that it just encompasses P, then the net current is zero since your question implies that the charge does not actually pass through the point P. In either case you have set up a scenario that violates the condition of the question, namely that the net current is a given value of I that, in general, is nonzero.

If the area of interest is such that Q passes through it on one leg but returns via a path that is outside the area of interest, then the charge that passes through the area is I·T. It doesn't matter whether the charge over time is made up of the same charged particles over and over or not. Also note that discussion assumes that we are talking about DC current.

 

It only now dawned on me that putting a charge on a capacitor requires pulling the electrons out of it. A Coulomb of charge is an absence of electrons. Never though of it that way until all this talk about sign conventions.

Well, pulling electrons out of one side (the side that becomes positively charged) and putting electrons in the other (the side the becomes negatively charged). Which is another inconsistency in the "electron flow" current. If you look in the E-book in the section on capacitors they have positive current flowing into the negative side of the capacitor when it is charging (getting a more positive voltage across it). Yet if you asked them the charge on each plate, they will apply a magical mystery minus sign and end up with a negative charge on the plate that they've been insisting has had positive charge flowing onto it.

 

Well, pulling electrons out of one side...and putting electrons in the other...

Ah yes, that's right. The net charge on the capacitor does not change. A "charge" on a capacitor is actually a separation of charge, giving us the storage of energy.