Flow of Electrons in a DC Circuit

[mtdoc]

You don't need to understand the nature of charge carriers to build a circuit, have a lifetime hobby in electronics - or even for a career in EE.

Very often we have people who have no idea on what is going on - and the conventional phrases are useful in building a functionally useful understanding.  Yes, they may be absolutely horrendous in regards to complete accuracy, but they are common terms that are frequently used, because the key concept is being communicated.  This is how I got the feel of how things worked and I was able to create success on the circuit in front of me.  Proper understanding followed later

Once they are comfortable with the basics and they are seeking to expand their understanding, then take things up a level - but at the moment, it is likely to confuse the hell out of a beginner, when it just is not necessary.

Yes. This. Absolutely.

Having spent 7 years of my life teaching introductory and more advance college courses (biology, physiology, neuroscience) I can tell you from first hand experience that no matter what field, any complex material must first be approached using imperfect analogies and carefully avoiding confusing students with caveats and divergence into first principles.  If you do they will absolutely "lose sight of the forest for the trees" and for many that will drive them away. For others their initial advancement will be stunted and incomplete because of the diversion.

I am (and have been for a few years now) a student of electronics, taking online courses, reading, playing with circuits, building and repairing. Because I have a technical background, and spent years using test equipment in an electrophysiology setting, I've been guilty myself of getting lost in the trees because I already knew enough about the underlying physics, etc to start following that path.

I have heard that argument before.  I believe that learning the correct terminology, definitions, and the correct way things work at the beginning helps eliminate the need to "relearn" the correct knowledge later.  Observe the multitude of folks who say and think that current flows.  Furthermore, learning the correct things at the beginning is not that much harder.

See above.   Complex subjects need to be broken down and oversimplified to begin then as understanding advances, caveats and more precise models introduced. It's incorrect to say that the time tested methods of teaching complex subjects involve teaching "incorrect terminology" or "incorrect knowledge".

I observed that most problems occur because the student does not have a good background of physics.  As you undoubtedly know, physics and math are the foundation sciences of electrical knowledge.

Yes, of course it helps if you already have had the foundational physics and math but it's been proven over decades that people without that - hobbyiests, hams, etc without a strong basic science foundation, can learn basic electronics, build functional circuits, have fun without that.  If they have a curious mind they will pick up the basics of these subjects along the way. They may eventually even delve into them in depth.

BUT - if you take an electronics beginner without that background and throw it at them from the outset you will only confuse them and perhaps drive them away.

The alternative is tell them "go take a college freshman level physics course and math through calculus then come back.."  Completely unnecessary and counterproductive IMO.

[rstofer]

BUT - if you take an electronics beginner without that background and throw it at them from the outset you will only confuse them and perhaps drive them away.

The alternative is tell them "go take a college freshman level physics course and math through calculus then come back.."  Completely unnecessary and counterproductive IMO.

Yes, the EE program requires Calc I to even get started; it's a prerequisite to EE101 in most universities.  Calc II (integral) is concurrent and Differential Equations is up next.  Of course, this is followed by the ever popular "Field Theory" and all that curl and divergence math I have never used.  If I had to make a living with my knowledge of Maxwell's Equations, I would have been living under a bridge!

None of that math is required for my hobby level involvement with electronics.  We do need to be able to apply Kirchoff's Laws from time to time but the circuits tend to be simple.  Or we model them with LTspice...

[james_s]

I use basic algebra quite a lot, but it's rare that I have to apply anything more advanced. Calculus comes in handy a little now and then but it's pretty rare that I have to actually solve any of that by hand.

[rstofer]

I use basic algebra quite a lot, but it's rare that I have to apply anything more advanced. Calculus comes in handy a little now and then but it's pretty rare that I have to actually solve any of that by hand.

That's pretty much my experience.  These days I am playing with wxMaxima for just about everything and it does a nice job of solving equations.  So much to learn...

[Ratch]

mtdoc,

Having spent 7 years of my life teaching introductory and more advance college courses (biology, physiology, neuroscience) I can tell you from first hand experience that no matter what field, any complex material must first be approached using imperfect analogies and carefully avoiding confusing students with caveats and divergence into first principles.  If you do they will absolutely "lose sight of the forest for the trees" and for many that will drive them away. For others their initial advancement will be stunted and incomplete because of the diversion.

It is not complex material that impedes students, it is the way it is taught.  Things like vague definitions (voltage is an "electric force") and using analogies as models ("think of electricity as a pipe full of water") are not too helpful.  Analogies should be used to make a point, not as a model for an alternative way things work.

I am (and have been for a few years now) a student of electronics, taking online courses, reading, playing with circuits, building and repairing. Because I have a technical background, and spent years using test equipment in an electrophysiology setting, I've been guilty myself of getting lost in the trees because I already knew enough about the underlying physics, etc to start following that path.

What does that have to do with what we are talking about?  Anyway, most of what a person who is proficient in a subject  knows, was learned on his own.  Teaching only got him started.

Complex subjects need to be broken down and oversimplified to begin then as understanding advances, caveats and more precise models introduced. It's incorrect to say that the time tested methods of teaching complex subjects involve teaching "incorrect terminology" or "incorrect knowledge".

Many of those time tested methods are in a rut.

Yes, of course it helps if you already have had the foundational physics and math but it's been proven over decades that people without that - hobbyiests, hams, etc without a strong basic science foundation, can learn basic electronics, build functional circuits, have fun without that.  If they have a curious mind they will pick up the basics of these subjects along the way. They may eventually even delve into them in depth.

BUT - if you take an electronics beginner without that background and throw it at them from the outset you will only confuse them and perhaps drive them away.

Learning a subject if more satisfying than fun.  A student must decide if he wants to have good knowledge of a subject or be a dilettante.

The alternative is tell them "go take a college freshman level physics course and math through calculus then come back.."  Completely unnecessary and counterproductive IMO.

If medicine were taught without the full background, we would be graduating witch doctors.

Ratch

[james_s]

It is not complex material that impedes students, it is the way it is taught.  Things like vague definitions (voltage is an "electric force") and using analogies as models ("think of electricity as a pipe full of water") are not too helpful.  Analogies should be used to make a point, not as a model for an alternative way things work.

Analogies like that are helpful to me in grasping basic concepts, and I know I'm not the only one. You can't see electricity, and for someone who is not particularly technical the water analogy works reasonably well. I'm a very visual thinker and never gathered much from theory and mathematical study and I struggled with a lot of math until I was able to visualize it in a practical sense and then it made sense.

This may not be helpful to you, but that doesn't mean it is not helpful to others.

[Ratch]

It is not complex material that impedes students, it is the way it is taught.  Things like vague definitions (voltage is an "electric force") and using analogies as models ("think of electricity as a pipe full of water") are not too helpful.  Analogies should be used to make a point, not as a model for an alternative way things work.

Analogies like that are helpful to me in grasping basic concepts, and I know I'm not the only one. You can't see electricity, and for someone who is not particularly technical the water analogy works reasonably well. I'm a very visual thinker and never gathered much from theory and mathematical study and I struggled with a lot of math until I was able to visualize it in a practical sense and then it made sense.

This may not be helpful to you, but that doesn't mean it is not helpful to others.

I hope no one gets wet using hydraulics as a teaching aid.  Do hydraulic engineers use electrical circuits to learn their craft?

Ratch

[Brumby]

I hope no one gets wet using hydraulics as a teaching aid.  Do hydraulic engineers use electrical circuits to learn their craft?

You are missing the point.

There is a reason the "water analogy" gets used in certain situations.  It is because the particular elements of whatever water construct used are visually obvious.  So obvious, in fact, that they can be more than adequately understood with a line drawing - and often, by just using one's imagination.  Your effort at a contra argument completely fails on this point alone.

[Ratch]

I hope no one gets wet using hydraulics as a teaching aid.  Do hydraulic engineers use electrical circuits to learn their craft?

You are missing the point.

There is a reason the "water analogy" gets used in certain situations.  It is because the particular elements of whatever water construct used are visually obvious.  So obvious, in fact, that they can be more than adequately understood with a line drawing - and often, by just using one's imagination.  Your effort at a contra argument completely fails on this point alone.

Simple electrical circuits can be easily imagined using Kirchoff's two laws.  No other analogies needed.  Hydraulics do not have fields, reactance, or binary flow (like holes and electrons) occurring at the same time.

Ratch

[Mr. Scram]

I hope no one gets wet using hydraulics as a teaching aid.  Do hydraulic engineers use electrical circuits to learn their craft?

People have no intuitive notion of electricity and associated forces. People generally have a very intuitive notion of water, pressure and flow. Comparing what is completely abstract with something you deal with every day helps understanding things quicker. Even things like current are shared between the analogy and the real thing.

Simple electrical circuits can be easily imagined using Kirchoff's two laws.  No other analogies needed.  Hydraulics do not have fields, reactance, or binary flow (like holes and electrons) occurring at the same time.

KCL can be more easily understood thinking of current as water flowing into and out of pipes. What's your point?

No one will claim that analogies do not break down sooner or later, but that does not render them useless. It does warrant a certain care, indeed.

[Ratch]

Mr. Scram,

People have no intuitive notion of electricity and associated forces. People generally have a very intuitive notion of water, pressure and flow. Comparing what is completely abstract with something you deal with every day helps understanding things quicker. Even things like current are shared between the analogy and the real thing.

If the teacher first explains that circuit current is charge particle movement along a conductor, he has everything he needs to build from there without referencing hydraulics.

KCL can be more easily understood thinking of current as water flowing into and out of pipes. What's your point?

I don't see how water movement is easier than particle movement.  Why change the medium?

Ratch

[Mr. Scram]

If the teacher first explains that circuit current is charge particle movement along a conductor, he has everything he needs to build from there without referencing hydraulics.

If I am asked to explain to a classroom of children or a random layman what electricity is and how it works, and I tell them what you just suggested, how many do you think have the faintest idea what I am talking about? I am willing to bet a fair amount of money you see them disengage from the conversation really quickly. If you use the water analogy, most will instantly grasp the basic concept, because it relates to something they already know. When those basics are established and electricity has become less alien, you can diverge into the specifics.

Teaching people effectively often consists of relating something new to something they already know. Very few concepts cannot be related to anything else, which are typically the subjects that people struggle with immensely. You do have to take care that the analogy is not extended to areas where it does not apply, but that should not be too much of an issue.

I don't see how water movement is easier than particle movement.  Why change the medium?

For reasons explained. If you sincerely do not see how it might be easier, I am not sure discussing this any further is useful. The horse has been led to water

[Brumby]

I would also like to point out that your tautological argument on the phrase "current flow" is, actually, quite wrong.  Yes, I will agree that the word "current" can be defined as "charge flow" - but after that, you have dropped the ball.

You are basing your argument on the appearance of the letters f-l-o-w next to each other.  You pay no heed to their specific usage and basic grammar.

The clue as to what is going on here - linguistically - is based in the very definition you, yourself, have presented - that (electrical) "Current" is defined as "Charge flow".

In this context, "current" is a noun and, thus, it's definition must also be equivalent to a noun - otherwise it wouldn't be a definition.  So "charge" and "flow" need to be taken as two inseparable halves of defining "current".  Looking at either word in isolation does not even begin to communicate the concept of current.  They must be considered as a single unit for the purpose of defining "current".

Now that we have a definition, let's use it....

We now look at electrical circuits and see charge moving around in mathematically describable ways.  So we can talk about the current in each part of that circuit.  But what happens when the mathematics say that there is no flow of charge in a particular section?

Conventionally, we say that the current is zero - but since your definition of current is immutably bound to the concept of "flow" being a real verb with all the powers of a verb on its own, the definition falls down.  The term "current" has no meaning.  We are simply looking at "charge".  Try floating that into a beginners understanding and see them howl in anguish - or run for the hills.

I was going to include the alternative conventional phrase that "no current flows" in such a case - but that seemed too much of an assault on the definition.

Once we adopt the term "current" as a noun in its own right, we can then use verbs with it to convey useful information.  You might object to the term "current flows", but I expect you would be OK with "current exists" yet, when it comes down to the key issue of communication, the basic concept is identical.  The use of the term "current flows" is descriptive - it follows the fundamental concept of electrons moving along, usually in a confined corridor, just like water down a stream.  The term "current exists" is far less descriptive and depends on a clear understanding of the definition of "current" before you can appreciate what is meant and only then can you look at applying it to the circuit.  It's like going back to first principles every time you look at an instance of the subject matter.  Sure, you'll get good at it after a while, but that's only if you stick with it.


As others have pointed out, the idea of teaching - especially beginners - is to condense out only that information which is necessary to give a functional understanding and is according to their ability.  If the subject is physics, then by all means throw in quantum mechanics.  If the subject is mechanical engineering, then by all means include the chemistry of corrosion - but no matter what the discipline, you cannot succeed in teaching if you spend inordinate amounts of time labouring over points that are, in the big picture, comparatively insignificant.

It is clear you are not a teacher.

Edit:
Having read the posts made whilst typing the above, I will repeat: It is clear you are not a teacher.

[Brumby]

To the OP, I have this to say:

Dear OpenCircuit,

Your original question was a good one.  You have acknowledged some of the posts made in reply, which should mean you now have your answer.  Take that knowledge and move forward.

You can ignore the rest of this thread without having missed out on anything of any real importance.


Cheers.

[Ratch]

Mr. Scram,

If I am asked to explain to a classroom of children or a random layman what electricity is and how it works, and I tell them what you just suggested, how many do you think have the faintest idea what I am talking about?

It would depend on their age, wouldn't it?  I would not attempt to teach something like that to children too young.  Most kids have experience with electrical appliances as well as a water faucet.

Teaching people effectively often consists of relating something new to something they already know. Very few concepts cannot be related to anything else, which are typically the subjects that people struggle with immensely. You do have to take care that the analogy is not extended to areas where it does not apply, but that should not be too much of an issue

I don't think it is needed in this case.

For reasons explained. If you sincerely do not see how it might be easier, I am not sure discussing this any further is useful. The horse has been led to water.

Easier and wrong.  You are right.  I am not convinced.

Ratch

[Mr. Scram]

As others have pointed out, the idea of teaching - especially beginners - is to condense out only that information which is necessary to give a functional understanding and is according to their ability.  If the subject is physics, then by all means throw in quantum mechanics.  If the subject is mechanical engineering, then by all means include the chemistry of corrosion - but no matter what the discipline, you cannot succeed in teaching if you spend inordinate amounts of time labouring over points that are, in the big picture, comparatively insignificant.

Daddy, what is electricity?
Well, my dear, let me tell you about quantum entanglement 

[Brumby]

Bazinga!

[rstofer]

I don't see how water movement is easier than particle movement.  Why change the medium?

Ratch

Because I can safely pour water out of a bucket and a shared experience will tell us how it's going to work out.  The youngest child, having spilled their milk, knows exactly what is going to happen.

It's just a place to start.

[Mr. Scram]

Easier and wrong.  You are right.  I am not convinced.

Conventional current is wrong. Quantum mechanics and relativity will not play nice, which means our current models are wrong. Our understanding of the universe in incomplete and wrong. Effectively, we should stop teaching people about anything because everything is wrong.

We are feeble monkeys in a freighting universe. We cannot hope to be right, especially if we are not prepared to be wrong at first.

[Brumby]

It's just a place to start.

Exactly so.

[Brumby]

Easier and wrong.  You are right.  I am not convinced.

Conventional current is wrong. Quantum mechanics and relativity will not play nice, which means our current models are wrong. Our understanding of the universe in incomplete and wrong. Effectively, we should stop teaching people about anything because everything is wrong.

We are feeble monkeys in a freighting universe. We cannot hope to be right, especially if we are not prepared to be wrong at first.

I imagine Ratch's response might be along the lines of - let's be right when we can.

Forget how encumbered we might become, throwing off conventional thinking and accepted jargon - even when the shortcomings they may carry with them are well known.  Let us drown in a sea of precision, even with life boats all around us.  They may not be ideal watercraft - but we can use them to survive and help us get where we are going.

[mtdoc]

It is not complex material that impedes students, it is the way it is taught. 

Yes, and teaching by at first simplifying and when necessary using analogies is a long proven method to teach complex material successfully.  That's what makes a truly great teacher: the ability to take a complex subject and simplify it in a way that allows a rank beginner to say "ah, now I get it!". Even if that simplification contains innaccuracies and ignores important caveats. There are plenty of college professors who aproach it the way you suggest and fail - most of them either don't care about teaching or have forgotten what it is like to have a "beginner's mind".

Learning a subject if more satisfying than fun. 

It should be both,otherwise it's being done wrong.

A student must decide if he wants to have good knowledge of a subject or be a dilettante.

That's a very arrogant attitude to take in a forum that is made up of not only professional EE's but also hobbyists of all knowledge and skill levels who are interested in learning and enjoying their hobby regardless of their background or how much time they have available to devote to it. This is the beginner's section for christ's sake !!

If medicine were taught without the full background, we would be graduating witch doctors.

Well, having been both a teacher of medical students and a medical student myself, I can say with absolute certainty that many subjects in pre-med and medical school are taught by beginning with over simplified and imperfect analogies and models. Many subjects never delve into underling first priniples and that is fine. Many imperfect, simplifed models of natural phenomenon prove perfectly adequate for practitioners in the real world - and that is true in many fields. Case in point: The example of using "conventional current flow" that arose from the OP of this thread.

[Mr. Scram]

I imagine Ratch's response might be along the lines of - let's be right when we can.

It helps to be wrong. It is exactly why Dave tells us he hopes our next project does not work.

[Brumby]

A student must decide if he wants to have good knowledge of a subject or be a dilettante.

That's a very arrogant attitude to take in a forum that is made up of not only professional EE's but also hobbyists of all knowledge and skill levels who are interested in learning and enjoying their hobby regardless of their background or how much time they have available to devote to it. This is the beginner's section for christ's sake !!

I'm glad you addressed this point.  I needed to give it some space before I even tried.

If medicine were taught without the full background, we would be graduating witch doctors.

Well, having been both a teacher of medical students and a medical student myself, I can say with absolute certainty that many subjects in pre-med and medical school are taught by beginning with over simplified and imperfect analogies and models. Many subjects never delve into underling first priniples and that is fine. Many imperfect, simplifed models of natural phenomenon prove perfectly adequate for practitioners in the real world - and that is true in many fields. Case in point: The example of using "conventional current flow" that arose from the OP of this thread.

The choice of medicine as a parallel was interesting - and entirely foolish, IMO.  Correct me if I'm wrong, but I am of the understanding that, as much as we have discovered about medicine, there is a great expanse of knowledge in this field that we do NOT know.

I am reminded of this:


Should I feel worried about seeing my local witchdoctor G.P.?

[Ratch]

Brumby,

I agree with the first five paragraphs of your post.

Now that we have a definition, let's use it....

OK.

We now look at electrical circuits and see charge moving around in mathematically describable ways.  So we can talk about the current in each part of that circuit.  But what happens when the mathematics say that there is no flow of charge in a particular section?

Conventionally, we say that the current is zero - but since your definition of current is immutably bound to the concept of "flow" being a real verb with all the powers of a verb on its own, the definition falls down.  The term "current" has no meaning.  We are simply looking at "charge".  Try floating that into a beginners understanding and see them howl in anguish - or run for the hills.

That is a good example of sophistic reasoning. Just because the flow is zero, it is still a valid value and its meaning is not changed.  You would not have a problem with a speed of zero and say its definition of distance per time is invalid, would you? Besides "flow" in not a verb in this case, it is a noun and charge is an adjective.  Just like "car speed".

You might object to the term "current flows", but I expect you would be OK with "current exists" yet, when it comes down to the key issue of communication, the basic concept is identical.  The use of the term "current flows" is descriptive - it follows the fundamental concept of electrons moving along, usually in a confined corridor, just like water down a stream.  The term "current exists" is far less descriptive and depends on a clear understanding of the definition of "current" before you can appreciate what is meant and only then can you look at applying it to the circuit.

"Current flows" is redundant, but, "current" is the exact descriptive.  Of course, you have to know what current is before you can appreciate it, don't you?  That is true of all words, isn't it?

Ratch