Dave and Thingmaker3,

Yes, I realize that you are all committed to electron charge flow specifying the direction of the current. But doesn't it bother you a little bit that in the OP amp circuit posted at the beginning of this thread, an ammeter will show just the opposite current direction that is indicated in the schematic? As well as being out of step with industry standards with respect to semiconductors and most of academia? You can call the moon green if you want, but it sure won't describe it better.

Ratch

 

How do you arrive at that? The output will be at +12 volts and the tail of the resistive divider chain is at ground. Those little electrons which are absolutely and unequivocally the sole carriers of charge in that circuit will be moving from ground (relatively negative potential) towards that +12 volt point.

Ammeter conventions were set in the days of vacuum tubes when conventional current was agreed on. Just like the directional arrows on diodes and transistors, they indicate the reverse of the actual electron movement.

Or are you maintaining that ammeters are really correct, and those are positive charges moving through the wires? That everything we know about electrons and the charge they carry is incorrect?

 

What do you mean by current not going anywhere?

Well, to quote your own words: "First of all, current does not flow."

----

It's probably pointless for me to continue in this discussion when I can't get the only person who agrees with me to agree with me, but I'll try one more time, with a hypothetical story:

It's the year 2050, and a new electronics component has been invented: ProtonWire

ProtonWire is unique in that it is composed of a chemical which allows protons to flow rather than electrons. Since this chemical is green in color (and also because I couldn't find a red pen) the schematic symbol for this component has come to be green lines rather than the conventional black.

Now look at the attached drawing.

I've labeled the current flow in this schematic according to how it would be labeled in the textbook, which is that whenever charged particles are flowing in the direction indicated by the arrow, that is a positive current, regardless of whether the particles themselves are positively or negatively charged.

Now doesn't it seem a bit strange to have the arrow on the ProtonWire pointing in the opposite direction of the other arrows. What's more, if it were pointing in the same direction, wouldn't it be strange to say that -50 mA was flowing at that point, but +50 mA was flowing everywhere else?

Conventional current makes perfect sense when you realize that it represents the flow of charge rather than the flow of electrons. When positive charge flows with the arrow, that is positive current, and when negative charge flows with the arrow, that is negative current.

Where the confusion arises is when you view the arrow not as an indication of the polarity of the measurement, but instead as an indication of the direction that particles are flowing in. Then you either want to reverse the arrows or you want to imagine holes flowing around, but both ideas are incorrect. The arrows simply don't indicate the direction of flow of anything.

 

How interesting. What happened to the electrons? The degree of disassembly to pry protons out of atomic nucleii is not for the faint of heart. All that atomic force having to be overcome? What of those liberated neutrons? All that binding energy inconveniently showing up?

If we really were moving positive charge carriers through the wires, then all the arrows would point correctly. But there would be no survivors around to appreciate the difference.

 

beenthere,

How do you arrive at that?

At what? I said several things in the previous post.

The output will be at +12 volts and the tail of the resistive divider chain is at ground. Those little electrons which are absolutely and unequivocally the sole carriers of charge in that circuit will be moving from ground (relatively negative potential) towards that +12 volt point.

That is correct, but the ammeter is manufactured to assume positive charges flow into the + end of the ammeter to indicate a forward direction. That makes it indicate the opposite direction for electron flow going into the positive lead. But worrying about the direction of the charge carriers is not necessary.

Ammeter conventions were set in the days of vacuum tubes when conventional current was agreed on. Just like the directional arrows on diodes and transistors, they indicate the reverse of the actual electron movement.

They were probably set before that. And it's a good thing they are set up that way. See below.

Or are you maintaining that ammeters are really correct, and those are positive charges moving through the wires? That everything we know about electrons and the charge they carry is incorrect?

No. How can you infer that? I am saying that the "real" charge carriers should not be use to reference the direction of the current for mathematical calculations. And the convention by which electrical components and test equipment are manufactured should be followed.

Now let's see what happens when and if they started making ammeters so that the current direction indicated is the opposite of what it is now. In other word, it indicates the "true" direction of negative charge carriers or electrons. So a technician measures the voltage of a battery at +1.5 volts. Then he switches to a high current range to measure the shorted current for an instant. He would have to switch leads to get a forward direction. How convenient!

Ratch

 

peajay,

What do you mean by current not going anywhere?

Well, to quote your own words: "First of all, current does not flow."

That is right, current IS flow. It does not flow twice. Charge can flow, however.

The arrows simply don't indicate the direction of flow of anything.

The arrows indicate ther direction orientation of the conventional current direction. In loop analysis, it is usually assumed that the charges move in a clockwise direction. An arrow in the opposite direction indicates that the current source has been reversed.

In your circuit, let's assume that we are electroplating copper. In the circuit you have drawn, we assume the conventional current is moving in a clockwise direction, which is opposite to the direction you drew the arrows. Clockwise is also opposite to the "real" direction of the electrons in the wire. Now we reach the electroplating solution designated by the green wire. Here the soluable copper gives up a electron which moves left on the top circuit. The positive copper ion is attracted to the negative voltage at the south end of the wire and accepts an electron while bonding to the metal. During the time the positive ions are traveling to the negative wire, the conventional current method really gives the "true" direction of the current, and the electron flow convention does not. Since there are just as many positive charges running around in the universe as negative charges, why say the conventional charge flow is wrong? I know you don't, but I have a hard time understanding your explanation.

Ratch

 

I have a hard time understanding your explanation.

Uhmm... Let me see how few words I can use, in hope that more attention will be given to each:

Electron current is negative current because electrons are negatively charged. Therefore, if you measure electron current, you must negate the measurement. The textbook fails to negate these measurements.

Hmm... No, I don't think that will do it.

To put it in a greater number of words:

I have no objection with the directions in which the arrows point. You can point them in any direction you like. What I object to is the sign of the measurement displayed next to them. When electrons are flowing in the same direction as the arrow, that is negative current, and so the measurement written next to the arrow should be negative, not positive.

The arrows indicate the polarity of the current measurement. As such, there are four possible scenarios:

positive charge flows with arrow: positive current
positive charge flows against arrow: negative current
negative charge flows with arrow: negative current
negative charge flows against arrow: positive current

With this arrangement, if you have a positive current, then the voltage at the destination that the arrow points to becomes more positive, regardless of the charge of the particles which are flowing.

The textbook, however, advocates this arrangement:

positive charge flows with arrow: positive current
positive charge flows against arrow: negative current
negative charge flows with arrow: positive current
negative charge flows against arrow: negative current

With this arrangement, if you have a positive current, you do not know if the voltage at the destination will become more positive or more negative unless you also know the polarity of the charges which are flowing.

Essentially, the entire debate between conventional current and electron current is a difference in opinion about what the arrow indicates.

Conventional current measurements assume that the arrow indicates the polarity of the current measurement, and that it indicates where an increase in voltage may occur as a result of positive current flow.

The textbook wants the arrow to indicate the direction of flow of particles, and requires that it be assumed that these particles are negatively charged so that it is known that the arrow indicates where a decrease in voltage may occur as the result of a positive current flow.

Yes, that is a fairly safe assumption, and so it is a useable model. It simply isn't an ideal model because it has an unnecessary inversion in the relationship between voltage and current. In the end, no one cares about what particles are moving in which direction. All anyone cares about is how currents affect voltages and how voltages affect currents. Conventional current measurement respects this. Electron flow measurement simply puts the electron on a pedestal and demands that we admire its negative charge.

------

To repeat myself in completely different words:

You just have to realize that "current" and "the flow of charged particles" are different things. "Current" is a measurement of the flow of charge. The sign of that measurement depends on two things; the polarity of the charged particles and the direction in which they are flowing.

Positive charges flowing with the arrow results in a current measurement with a positive sign.

Negative charges flowing against the arrow also results in a current measurement with a positive sign, because two factors were negated.

If you only negate one, however, then the sign of the measurement is negative.

Positive charges flowing against the arrow results in a current measurement with a negative sign.

Negative charges flowing with the arrow results in a current measurement with a negative sign.

The problem I have with the convention used in the textbook is that in that last situation, it gives the current measurement a positive sign, just because. It's mathematically incorrect.

 

peajay,

My head aches from trying to follow your reasoning. You will never get anything calculated if you have to puzzle out problems that way. You or anyone else should not get tangled up wondering about what the polarity of the charge carriers are, and which direction they move. You treat them all as positive charge carriers moving from positive to negative in calculations, even if the real charge carriers don't behave that way in that situation. Then you can worry about the real direction if necessary after obtaining the answer. If a resultant value for current is negative, then you have assumed the wrong direction in your calculations. Let the math do the work instead of you wondering about whether the real direction is correct.

Ratch

 

You or anyone else should not get tangled up wondering about what the polarity of the charge carriers are, and which direction they move. You treat them all as positive charge carriers moving from positive to negative in calculations, even if the real charge carriers don't behave that way in that situation.

That is essentially my point, but how does one explain that without "getting tangled up wondering about what the polarity of the charge carriers are, and which direction they move."

To truly explain the faults of electron current measurement, you have to explore it in its own domain. After all, if the idea were internally self-consistant, then the choice to use it would simply be a matter of preference rather than a matter of being incorrect.

 

peajay,

That is essentially my point, but how does one explain that without "getting tangled up wondering about what the polarity of the charge carriers are, and which direction they move."

I already explained how to do that many times.

To truly explain the faults of electron current measurement, you have to explore it in its own domain. After all, if the idea were internally self-consistant, then the choice to use it would simply be a matter of preference rather than a matter of being incorrect.

Once a person realizes that both of the two charge carriers can move, then s/he should realize that the direction of the charge flow should not be changed back and forth based on the real direction of the charge carrier being measured. The positive charge carriers were chosen to be the reference because of mathematical considerations. It is more intuitive that a positive current direction comes from a positive voltage. You write a lot less minus signs that way. And for that standardization reason, that is the way electronic components and equipment are manufactured to be used and installed.

Ratch

 

I should have read that.

No problem.

Dave and Thingmaker3,

Yes, I realize that you are all committed to electron charge flow specifying the direction of the current. But doesn't it bother you a little bit that in the OP amp circuit posted at the beginning of this thread, an ammeter will show just the opposite current direction that is indicated in the schematic? As well as being out of step with industry standards with respect to semiconductors and most of academia? You can call the moon green if you want, but it sure won't describe it better.

Ratch

Not bothered at all. The author gives a treatise of conventional vs electron flow current and states that the convention used throughout this material is electron flow in order to understand the physicality of what is happening; this e-book is to learn the basics not a blueprint for industry. If no distinction was made, I would be bothered.

A well versed student in this subject will, by the end of their studies (whether formally or through reading this e-book), have sufficient understanding to decipher conventional vs electron notation in technical literature and determine the information given from measurement devices.

Dave

 

But doesn't it bother you a little bit that in the OP amp circuit posted at the beginning of this thread, an ammeter will show just the opposite current direction that is indicated in the schematic?

Why would it bother me? I have maintained for decades that electrons don't care what color plastic we have on the outside of the wires.

If it bothered me, I would simply swap the red and black leads.

Poh-TAYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY-toh

Poh-TAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAHH-toh.

Does not bother me at all. Seems to bother you, though. Whatever will you do about it?

 

thingmaker3,

Does not bother me at all. Seems to bother you, though. Whatever will you do about it?

Doesn't bother me. I know what is going on. Seems to confuse a lot of folks, however. There has been and will be a lot of bandwidth expended and a lot of clarfication to explain what is happening.

Ratch

 

So in a circuit diagram, you see a current source with an arrow pointing up.

Which end is positive in most textbooks?

Which end is positive in the eBook?

 

thatoneguy,

So in a circuit diagram, you see a current source with an arrow pointing up.

Which end is positive in most textbooks?

Which end is positive in the eBook?

Positive with respect to voltage or current?

Ratch

 

A Current source in parallel with a 10 Ohm resistor.
Arrow is pointing up.

What would the polarity of the voltage across the resistor be in the following two situations:
a) Basic Electronics book
b) AAC Online book

Sorry for not being clear. I'm simply trying to visualize the "discrepancy" with regards to the original op amp schematic.

 

thatoneguy,

A Current source in parallel with a 10 Ohm resistor.
Arrow is pointing up.

What would the polarity of the voltage across the resistor be in the following two situations:
a) Basic Electronics book
b) AAC Online book

I hate to be coming back to ask for clarification again. Since the ebooks are large, could you post a link to the section you have in mind. As for the paper text book, I am assuming it to follow conventional current.

Sorry for not being clear. I'm simply trying to visualize the "discrepancy" with regards to the original op amp schematic.

The discrepancy is that if you insert a ammeter with the + terminal on the OP amp output, it will indicate positive current going in a right to left direction, which is in a opposite current direction than the OP amp schematic posted at the beginning of this thread. So the ammeter shows the opposite current direction than the schematic does. All ammeters are conventional current responding. One should always be able to rely on the ammeter to determine the current direction, and not have to mentally or physically switch leads.

Ratch

 

I have an Egyptian friend who can reads his Qur'an in Arabic from right to left, and then instantly pick up and read an English book from left to right.

Years ago I visited him in Egypt and I witnessed him speak in three languages simultaneously. We were walking in a market street speaking English and stopped at a vendor. He bargained with the owner for me in Arabic, and while this was happening, a tourist started speaking to him in French. I was impressed.

Some people detest change, while others revel in it.

 

thatoneguy,
I hate to be coming back to ask for clarification again. Since the ebooks are large, could you post a link to the section you have in mind. As for the paper text book, I am assuming it to follow conventional current.

I wanted to make sure it wasn't misleading, so I worded it as simple as possible as a hypothetical question. I couldn't find a current source in the eBook. "Current Source" search shows zero results. I looked at the common areas where one would be shown in a schematic, and saw blank circles with polarity markings. So, no arrow.

The question is, if a CCS were to be drawn in in the eBook, would the arrow would need to be pointing downward, rather than upward (industry standard, just like diodes), to indicate "Standard Polarity".

In short, although you are hopelessly pedantic, I agree with you on this.

Generally, most other "beginner sites" on the web depict and use conventional current for math. Somebody who doesn't know the complete theory and reasoning can easily get VERY confused, and come to believe that either the book is "wrong", or "all the other sites are wrong", as observed in the original post.

We can do the math either way. I'd like beginners to have an easy time of it, personally, since there's plenty of time to completely mess with their heads later on.

I would suggest that an abbreviated "Statement of Standards used" be added to the TOP of every page containing a depiction of current flow. Many people will hit a certain page from google, and when they see arrows going the wrong way, they aren't going to hunt for an introduction or ask, they'll just leave.

I'm not trying to be difficult, and I highly respect and admire the work the authors have put into the book. This is just the THIRD TIME it's come up in the very short time I've been a member, so I believe it needs to be addressed, somehow.

 

It is apparently one of those things that present problems for some people. I always thought that once you learned that it was electrons that carried the charges, the question was forever settled. "Conventional" current is confusing, as it is incorrect.

To speak of a "positive" versus a "negative" current seems absurd. It's simply current - electrons moving charge from a negative voltage point to a more positive voltage point, with the voltage difference providing the energy to force the movement.