Hi,

Analogies are good for a quick rough explanation as to how something works, but they almost always break down at some point. The water/pipe analogy works to a certain point but of course it's not exactly the same just like any other analogy. Water is considered incompressible in many problems but with impurities pressure applied at one point still takes time to propagate to another point. Electrons are also considered incompressible so 'pressure' applied at one point should propagate to another point instantaneously, but we know that isnt true either. A signal applied to an electron in Los Angeles would take around 16ms to reach New York, and the return signal would take another 16ms to get back (ideal transmission line with the lowest possible coefficients). That's not instantaneous either so we have to think that during the first instant there are more electrons in the transmit wire than in the return ground wire. That is similar (not exact of course) to the way water works when we turn on the faucet except we are looking at much longer time delays where we might fill up a gallon jug of water and keep it on the shelf for years before using it to wash clothes and then it ultimately returns to the 'ground'. Some of it may vaporize and then fall as rain also returning to the 'ground'.

So analogies are great and they have helped us understand things for years, but taken too far and we have to start really thinking and in some cases it's not going to carry over without really stretching the imagination. It's best to mention the shortcomings as soon as the analogy is given so there is no surprises later.

Another example is the transistor as a 'switch' We all know a transistor can not be a perfect switch, yet it makes sense to explain it that way to people who are just learning about transistors especially when used as switches. We talk about it like it is a switch, but then later make sure we mention that there is always some resistance. The analogy serves its purpose. Its purpose is to supply us with a little information at a time so we dont have to learn about the entirety of physics (or anything else for that matter) all in one sitting, which would be impossible for all but the simplest of concepts.

 

Let me see if I can help. There is quite some confusion when using the water analogy, so I wont. Electrons are free to move in a wire, because for example, copper atoms are able to let an electron "escape" when they form the metal structure. They are not free to move in a plastic, because the carbon-hydrogen bonds keeps them in check, and they can't escape. Thermal energy (heat from room temperature will do this) gives electrons enough energy in a copper wire to move at a very high velocity, something like 100,000 m/s, but don't travel far before hitting an atom, losing their thermal energy and thus maintaining an equilibrium.
In a wire there are millions x millions of electrons spread out along its length. In a circuit, a battery applying a voltage at one end pushes the electrons into that end of the wire (let's assume this is attached to the negative). The imbalance in charge in the wire creates an electric field. This travels as fast as it can, near the speed of light (depending on the characteristics of the wire) and as it does so the number of electrons in the wire increases. That is the wire charging up to the voltage which was applied. Individually, the number of electrons has hardly increased at all (this is dependent on the capacitance of the wire) but in effect, the field simply shunted them up a little, and the current flowing into the wire maintained the new number - the electrons themselves would not have had time to reach the far end from the start.If a current flows as a result of this battery, then the electrons move slowly around the wire, at walking pace. But the electric field propagates the charge so fast that if you connected a long pair of wires with a bulb at the far end to a battery, electrons are sucked out from the wire connected to the positive at the same rate they enter from the negative on the negative wire. That means the lamp does not actually light until a fraction of a second (a few ps) later. The relatively slow motion around the wire is then the "drift velocity".

Imagine a train of carriages with passengers forming a long line down the middle from the end of the last carriage to the front. A pusher pushes another passenger in at the end. Almost instantly, all passengers are shoved forward, and one falls out at the front, but the end guy can only move dead slowly down the train, as the line moves forward. Does that help?

 

Let me see if I can help. There is quite some confusion when using the water analogy, so I wont. Electrons are free to move in a wire, because for example, copper atoms are able to let an electron "escape" when they form the metal structure. They are not free to move in a plastic, because the carbon-hydrogen bonds keeps them in check, and they can't escape. Thermal energy (heat from room temperature will do this) gives electrons enough energy in a copper wire to move at a very high velocity, something like 100,000 m/s, but don't travel far before hitting an atom, losing their thermal energy and thus maintaining an equilibrium.
In a wire there are millions x millions of electrons spread out along its length. In a circuit, a battery applying a voltage at one end pushes the electrons into that end of the wire (let's assume this is attached to the negative). The imbalance in charge in the wire creates an electric field. This travels as fast as it can, near the speed of light (depending on the characteristics of the wire) and as it does so the number of electrons in the wire increases. That is the wire charging up to the voltage which was applied. Individually, the number of electrons has hardly increased at all (this is dependent on the capacitance of the wire) but in effect, the field simply shunted them up a little, and the current flowing into the wire maintained the new number - the electrons themselves would not have had time to reach the far end from the start.If a current flows as a result of this battery, then the electrons move slowly around the wire, at walking pace. But the electric field propagates the charge so fast that if you connected a long pair of wires with a bulb at the far end to a battery, electrons are sucked out from the wire connected to the positive at the same rate they enter from the negative on the negative wire. That means the lamp does not actually light until a fraction of a second (a few ps) later. The relatively slow motion around the wire is then the "drift velocity".

Imagine a train of carriages with passengers forming a long line down the middle from the end of the last carriage to the front. A pusher pushes another passenger in at the end. Almost instantly, all passengers are shoved forward, and one falls out at the front, but the end guy can only move dead slowly down the train, as the line moves forward. Does that help?

Hi,

That argument assume prefect rigidity which is not a physical possibility especially among groups of objects because there is always some elasticity. The elasticity causes a delay in propagation just like in a transmission line. So for one person pushing another there is only a tiny delay before the second person moves, but for a million people the delay could be long because of the elasticity. In a small electronic circuit this shows up as inductance.

I think at present the only thing that violates this principle is quantum entanglement.

 

Hi,
That's not instantaneous either so we have to think that during the first instant there are more electrons in the transmit wire than in the return ground wire. That is similar (not exact of course) to the way water works when we turn on the faucet except we are looking at much longer time delays where we might fill up a gallon jug of water and keep it on the shelf for years before using it to wash clothes and then it ultimately returns to the 'ground'. Some of it may vaporize and then fall as rain also returning to the 'ground'.

That's another IMO misleading idea that's due to the water analog to explain electrical energy and electricity. What's the transmit and return wire for energy in a circuit? Is it the + or - from a battery, what about AC current? In most circuits that don't radiate there is always a equal and opposite force as the initial impulse travels down the circuit on both wires. If in the first instant there are a few more electrons on one side relative to some point there are also a few less electrons on the other side relative to some point as the electric field moves. The total number of electrons (charge carriers) in the entire circuit loop doesn't change, it's their separation at points in space that matters. It's the potentials from charge separation that cause energy flows, not the current in most circuits. Physical moving current is important because it gives rise to the magnetic field we use in transformers to transmit energy across space as a common example. Normally we use current as a proxy for the magnetic field in circuit theory because it's not as easy to directly measure as current. We also use current as a proxy for power in most AC utility circuits because the voltage is a fixed constant in the power calculation. Just because we do these things to make it easier doesn't change the true nature of current as a movement of charge, not a movement of electrical energy.

 

Hi friends,

This question may sound a bit strange, and maybe I wont put it right enough, but do you believe that there is something really flowing inside wires, i.e. the thing called current ?

I mean, I have a feeling that electrons don't really flow inside the wire, and it's more like a wave of something that propagates, but without actual flow of anything, if you know what I mean. We have a tendency of thinking that everything is like little balls moving about, but when you get down to a micro level, I think these notions break down.

I am not a physicist so I might be talking nonsense........ Well

Do you believe that electrons really are like small clouds or balls moving around ? Or are electrons something else?

In fact, is it the electric and magnetic fields that move like waves inside the wires? It could be that its just the fields that move, and not the electrons.

This would mean the notion of current is flawed in some way? If there arent really little balls flowing, then how can current make sense?

Isn't current just a macro construct to understand circuits?

There are TWO different current flows. The important one is the flow of energy, which is nearly the speed of light. The other kind is ELECTRON DRIFT, which is extremely slow....about an inch per hour at 1A in 14 gauge wire.

In a vacuum tube, the actual electron drift can be quite fast....a large fraction of the speed of light. But that's a special case. In a conductor the two flows are very different

 

There are TWO different current flows. The important one is the flow of energy, which is nearly the speed of light. The other kind is ELECTRON DRIFT, which is extremely slow....about an inch per hour at 1A in 14 gauge wire.

In a vacuum tube, the actual electron drift can be quite fast....a large fraction of the speed of light. But that's a special case. In a conductor the two flows are very different

Other than electron tubes and a few specialized devices the flow of energy in a circuit is not a current flow of any type. Electrical energy flows as fields in the space around the conductors. Kinetic energy flowing in conductors is usually wasted as heat. In electron tubes the gained kinetic energy of electrons is usually converted to heat or x-rays when they strike the anode. DC circuits produce electric and magnetic fields but they don't create electromagnetic waves other than a brief blip when first turned on or off due to rapidity changing fields.

http://amasci.com/elect/poynt/poynt.html

Sure, we can compute and use current as a energy flow proxy because we use speed of light cause and effect for current in circuit theory as a simplification of field theory calculations of magnetic fields.

 

That's another IMO misleading idea that's due to the water analog to explain electrical energy and electricity. What's the transmit and return wire for energy in a circuit? Is it the + or - from a battery, what about AC current? In most circuits that don't radiate there is always a equal and opposite force as the initial impulse travels down the circuit on both wires. If in the first instant there are a few more electrons on one side relative to some point there are also a few less electrons on the other side relative to some point as the electric field moves. The total number of electrons (charge carriers) in the entire circuit loop doesn't change, it's their separation at points in space that matters. It's the potentials from charge separation that cause energy flows, not the current in most circuits. Physical moving current is important because it gives rise to the magnetic field we use in transformers to transmit energy across space as a common example. Normally we use current as a proxy for the magnetic field in circuit theory because it's not as easy to directly measure as current. We also use current as a proxy for power in most AC utility circuits because the voltage is a fixed constant in the power calculation. Just because we do these things to make it easier doesn't change the true nature of current as a movement of charge, not a movement of electrical energy.

Hi,

Well it does not matter if we look at both wires or just one wire when we talk of just the number as being greater than or less than the other wire because that involves both wires anyway, and i just happened to mention what happens in one wire while you are talking about that happens in both wires. That's fine too though, but that does not change the relative number in one wire than the other wire, and it does not change the situation when we say that there is more spacing in one wire than the other because spacing changes the relative number and the question of the relative number in each wire was already addressed.

The real point here is that the termination does not see any change until after a delay, and that can be viewed as elasticity and that's just what inductance does and so this should not be too much of a surprise. The delay may occur in both wires at the same time, but the delay is still present.

It's also true that the field starts everything moving and there is no analog for water in a pipe, but that's the way analogies are, they are never perfect because by definition an analogy is not an exact replica of the original subject matter.

 

Hi,

Well it does not matter if we look at both wires or just one wire when we talk of just the number as being greater than or less than the other wire because that involves both wires anyway, and i just happened to mention what happens in one wire while you are talking about that happens in both wires. That's fine too though, but that does not change the relative number in one wire than the other wire, and it does not change the situation when we say that there is more spacing in one wire than the other because spacing changes the relative number and the question of the relative number in each wire was already addressed.

The real point here is that the termination does not see any change until after a delay, and that can be viewed as elasticity and that's just what inductance does and so this should not be too much of a surprise. The delay may occur in both wires at the same time, but the delay is still present.

It's also true that the field starts everything moving and there is no analog for water in a pipe, but that's the way analogies are, they are never perfect because by definition an analogy is not an exact replica of the original subject matter.

I mainly agree with your answers and it's another reason why talking about electrons or analogized substitutes for electrons as energy carriers in circuits has limited value even if it simplifies.

The sad thing about this simplification is that generations of students of electricity actually have no idea how electrical energy really works.

 

Yes Virginia, the current does flow. By definition too.

Current is defined as the passage of charge past a given point (or surface for a wire) in a given time. When approximately 6.242×1018 electrons pass this place in one second a current of 1 ampere is flowing.

For a DC current they really do move, albeit slowly. In an AC current the electrons wiggle back and fourth over a small length.

The only analogy I find useful to describe this is to imagine the elections in a conductor as a gas free to move due to the electric field.

Finally, since the definition of a positive current is in terms of a positive charge passing thru the surface, then a negative charge going the opposite direction will also be a positive current, as you have a change in sign in both the direction, and the charge.

<mic drop>

 

The only analogy I find useful to describe this is to imagine the elections in a conductor as a gas free to move due to the electric field.

Which is functionally identical to water in a pipe free to move due to a pressure differential.

 

MrAI
- I agree that the line of people analogy might not be quite right. There is not a really good analogy for electricity, but the water works is not bad.
"Instantaneous" might be wrong but 2/3 the speed of light, a typical propagation speed down a transmission line, means that along a train line
of maybe 100m the propagation delay is about 0.5us. That is a lot quicker than most people would notice.
What I was trying to do was to give some sort of concept to someone who maybe is trying to understand.

 

MrAI
- I agree that the line of people analogy might not be quite right. There is not a really good analogy for electricity, but the water works is not bad.

I agree it's not bad, just poor because it's loaded with descriptive models that can cause deep misconceptions about even simple DC circuits in students unless they understand (unlikely) closed-loop systems or even simple pressure drops in water flows.

To most of us here these things (line loss, pressure drop, and flow) are second nature but I wonder how actually useful it is with new students. It is very important to point out to students that this water circuit is actually different to the domestic water supply. By the time one explains these concepts for hydraulics, it would seem more prudent just to explain the electrics.

https://web.stanford.edu/~danls/interactive analogies.pdf

Electricity is a particularly hard domain to comprehend because there are few visible features to help create a model of electrical behavior. The electrical engineering students we have worked with can often provide quantitative solutions to problems by using formulas like Ohms law. But, we have found that most of them are unable to describe a systems level behavior of a circuit in qualitative terms. Moreover, they often rely on analogies they are taught in class that, because of their partial nature, only cause deep misconceptions. Good examples come from problems where we used a simple flashlight [see Fig 1] consisting of two batteries, a switch and a bulb. We asked questions like “Where should you place a fuse to protect the expensive halogen light bulb?” or “What happens to the voltage and current if we change the bulb from a 5 Watt value to a 10 Watt bulb?
...
Many students insist a fuse must go between the positive terminal of the battery and the bulb because when the current flows through the switch it will “blow” the fuse before it reaches the light bulb. This is wrong. The idea of current flowing through the wire sequentially is like filling an empty pipe up with water. Students make their mistake because they have not had a chance to make the correct analogy between the water flow analogy they were taught and electricity. The proper analogy is that the circuit acts more like a full pipe of water. Because water cannot be compressed very well, a flow in one part of the circuit causes a simultaneous change in all parts of the circuit. Therefore, the amount of current that flows is a function of the components in the closed system, and the current is the same amount throughout the circuit as soon as the switch is closed. To protect the light bulb it doesn’t matter if the fuse is before or after the bulb.

The first relates to deciding when to rely or not rely on an analogy. As stated earlier, the mapping between analogies is not always perfect. Part of learning to use an analogy is knowing the occasions where the analogy works. Some errors occur because people do not realize an analogy has broken down.
...
A second class of limitation occurs when neither simulation provides the particular insight one needs to move ahead. Even in situations where the analogy between two systems is very close, the prior knowledge of the learner is insufficient. For example, one participant struggled to explain why there was a pressure drop across the valve and paddle wheel. He could correctly configure the electrical system to demonstrate the analogous voltage drop across the switch and light bulb. He recognized that this was a clue toward solving it, but could not describe why this phenomenon would occur in these systems.

https://pdfs.semanticscholar.org/56d2/230c4f9fdb8409f897220aedc959ff4f365d.pdf

However, it is very important to emphasize that analogies can be useful but if they are not well-chosen could give incorrect information to students, or even create further alternative conceptions and confusion. It is therefore essential to advise teachers to always remember that when they describe what electricity is like, they should use useful and appropriate analogies for the learners to form an appropriate understanding of the construct.
...
To ensure conceptual understanding of electric resistance, battery, current intensity, electric charges, electric field, an emf, a conceptual problem (experiments) was used to conceptualise these concepts. This analogy is related to a move from contextual to conceptual development of ideas. In this study, the students were given a bicycle analogy and the first researcher discussed with them how energy is transferred when a bicycle is pedaled. When the bicycle is pedaled or when the pedal is pushed with a constant force, against constant obstacles (i.e. electrical resistance), the flow rate of the wheels (current intensity) will be the same at each point. The pedals (i.e. source of energy = battery) maintain the movement by tiring the muscles (energy exhaustion of the battery). The chain which serves as a link (it is like electric charges) moves slowly but the energy (the pushing on the pedal) is instantly available. The energy is only transferred from the source (pedal) to the user (wheels) when the links move. The links never get lost or are used up and this is how Law of Energy Conservation was introduced, and the concept of electric field was also brought in. It was explained that a battery / cell is a devise which separates positive (+ve) and negative (-ve) charges – and the charge separation in the cell sets up an electric field between the opposite charges. Further discussion was conducted to make it clear that when a disaster happens, such as the chain breaking, the wheel of the bicycle would still rotate for a short while, thereby still supplying energy to the system. In applying this example to the notion of electrical circuit they could understand that the bulb may appear to continue shining for a short while (filament dying out) after its source of electricity has been cut off. Somehow, this contradicted their normal experiences with electrical switches, whereby the light instantly goes off as soon as the switch is turned off.
...
The results of this study have revealed the effectiveness of the intervention in helping students perform well on the topic ‘electric circuits which was also found by Gokhan et al, (2012) Indeed, the bicycle analogy used in the study seems to have successfully guided the students to construct scientifically acceptable notions of electricity and electric circuits. The high gains achieved by students illustrated the success of the intervention in effecting conceptual change towards the correct scientific conceptions.To this end, this study has succeeded in achieving its objectives, thereby making a significant contribution to both theory and practice.

 

I mainly agree with your answers and it's another reason why talking about electrons or analogized substitutes for electrons as energy carriers in circuits has limited value even if it simplifies.

The sad thing about this simplification is that generations of students of electricity actually have no idea how electrical energy really works.

Hi,

Yeah i guess it is the breakdown of the way schools teach stuff these days.
A good course would teach things properly and in a logical order.

I mainly talk about the water flow analogy when someone shows that there is no way they would be ready to understand fields and stuff like that. You'll notice that probably 99 percent of the talk on this site never gets into anything about a field of any kind. That's because in a lot of circuit analysis we never need it.
In fact something came up about a related issue yesterday. Someone took a test on some electronics site and did not get the right answer to what a 'hole' was (semiconductor). It is then that i realized that of all the people i knew in my lifetime there may be only 1 percent of all of them that needed to know what a hole was in order to perform their every day work, and many of them were engineers already or studying to be.
The simple truth is very few people have to understand quantum theory even at the most basic level like how an electron flows and what a hole is. It's more of a curiosity than anything else because they dont work with solid state physics in their every day work or even in their hobbies.

But i guess more to the point of the thread is that a newcomer to electrical circuits wants to get some kind of grasp on what is basic to circuit theory without having to go into the depths of physics. I also find that when i try to explain the shape of a field to some people they act like i am nuts or something that there could be something invisible to the eye that is that unique and real. I wonder if they go away in disbelief that there really is anything really that is known as a field.

 

But i guess more to the point of the thread is that a newcomer to electrical circuits wants to get some kind of grasp on what is basic to circuit theory without having to go into the depths of physics. I also find that when i try to explain the shape of a field to some people they act like i am nuts or something that there could be something invisible to the eye that is that unique and real. I wonder if they go away in disbelief that there really is anything really that is known as a field.

Sure. I just think there needs to be a physics consistent analogy used in circuit theory today that easily leads to a more physics based understanding of electricity. I'm training my now 12yo girl about electrical energy and physics. I was surprised how easy it was her to integrate electrical energy concepts using fields (attracting and repulsing over distance) because she had seen invisible forces used in modern CGI with superheros so to her there was no leap of intuition they could be real, invisible and powerful.

You don't need much mathematical rigor for basic rules.

 

It never ceases to amaze (and amuse) me watching how respectable, and knowledgeable members of this forum can still have some disagreements regarding the fundamentals of electricity... it tells me that some subtle concepts are not so easily grasped by the average person because they're things that lie outside of our everyday experience, and cannot be fully described through analogies, or even through what most of us regard as "common sense".

The way I see it, electrical science stands apart, and can only be understood through the equations that define it, atomic theory, and a little quantum mechanics...

This is a learning site indeed... I love this place

 

It never ceases to amaze (and amuse) me watching how respectable, and knowledgeable members of this forum can still have some disagreements regarding the fundamentals of electricity... it tells me that some subtle concepts are not so easily grasped by the average person because they're things that lie outside of our everyday experience, and cannot be fully described through analogies, or even through what most of us regard as "common sense".

The way I see it, electrical science stands apart, and can only be understood through the equations that define it, atomic theory, and a little quantum mechanics...

This is a learning site indeed... I love this place

The truth is most don't work in areas of electrical science that requires some detailed knowledge of the messy physics details on a daily basis (semiconductor material science) so they have incredible expertise in other areas of electrical science. The applied physics you need for making electronic devices is different but overlaps what's needed to use those created electronic devices in circuits. Most of the disagreements are not about absolute right or wrong, they are about the level of abstraction we should use when looking at problems that need solutions or teaching newbies how to create mental patterns of circuits. The main reason I don't like the water analog (especially the open-loop gravity version) is that water (current) is seen as the deliverer of power in most electronic–hydraulic analogy examples. It causes a subtle framework disconnect to the fundamentals of electricity and the relationship of energy flow to voltage, current and power that easily shows its face when we get to AC circuits and non-instantaneous transmission times across space like in RF energy movements. The source of energy and its movement in circuits is the key to simplifying fundamental electrical problems to their core and is IMO unfortunately wrongly placed in most analogies.

Yes, current does really flow but it doesn't have the effect during that movement that a lot of people think it does.
https://en.wikipedia.org/wiki/Hydraulic_analogy#Limits_to_the_analogy

In a hydraulic transmission line, the energy flows as mechanical waves through the water, but in an electric transmission line the energy flows as fields in the space surrounding the wires, and does not flow inside the metal.

 

It never ceases to amaze (and amuse) me watching how respectable, and knowledgeable members of this forum can still have some disagreements regarding the fundamentals of electricity... it tells me that some subtle concepts are not so easily grasped by the average person because they're things that lie outside of our everyday experience, and cannot be fully described through analogies, or even through what most of us regard as "common sense".

The way I see it, electrical science stands apart, and can only be understood through the equations that define it, atomic theory, and a little quantum mechanics...

This is a learning site indeed... I love this place

Hi,

The whole thing lies in the analogies. We are always using analogies but some people do not like analogies at all and try to never use them at all. We cant escape using them and to do so is to confuse at least for a time.

It's also interesting that in the non micro world when we push on something we get something to move, then taht might push on something else, etc. In the wire world, the field may do all the pushing. It's interesting though that DC current keeps flowing after seemingly only one application of force.

There's a lot to talk about though unfortunately, and that's where the analogies help convey the sub information so that someone can grasp it little by little. When we are taugh Ohm's Law for the first time we dont usually get the field thrown at us right away. Most circuit analysis books only go into a very light discussion of anything other than pure current flow as an entity in it's own right. They talk about charge movement without a deep explanation of why this happens. Now a physics book on the other hand must as a rule talk about this because that's what physics is all about, but circuit analysis is a separate thing that is usually handled differently in a circuit analysis book because there are concepts upon concepts that do not require knowledge of the field. IN fact, that's the main tipping ponit: if knowledge of the field is not reqwuired in order to use the concept being talked about, then facts about the field are left out. That's the way many things are.
For example, when we analyze a circuit with three resistors and a voltage source we dont need to konw anything about the field unless there is a good reason for knowing that. Even when talking about something as complicated electrically as a transmission line we dont have to know the field in most cases. Sure if we wanted to build a fusion reactor we'd have to know how the field works to some very high degree of accuracy, but even people doing such a thing have a hard time with that.

So there's a lot to talk about and it cant be done in one sentence so we have no choice but to use analogies until such time as we use more exacting descriptions and even then we still have to use analogies because we have no intimate contact with electrons or other sub atomic particles. Theories themselves are like analogies although we try to get as close as possible to what we call 'real' life, but what this really means is we come up with math descriptions that reflect what experiments have shown. Up until this point in time we dont even have all that right or explained completely, so we stick to analogies. For example, try to explain how a particle can seem to go back in time to modify it's behavior at the current time.

But back to the field. There are many many books written without the need to go into the field itself. Those are the circuit analysis type books. There are many books written about the field itself, and those are physics books.

 

But back to the field. There are many many books written without the need to go into the field itself. Those are the circuit analysis type books. There are many books written about the field itself, and those are physics books.

and there are a few good books that easily allow you to understand just how important a field based view of circuit analysis is.
http://onlinelibrary.wiley.com/doi/10.1002/0471433934.fmatter/pdf

This book provides a new way to understand the subject of electronics. The
central theme is that all electrical phenomena can be explained in terms of
electric and magnetic fields. Beginning students place their faith in their early
instruction. They assume that the way they have been educated is the best
way. Any departure from this format just adds complications. This book is a
departure—hopefully, one that helps.
There are many engineers and scientists struggling to function in the real
world. Their education did not prepare them for handling most of the practical
problems they encounter. The practitioner in trouble with grounds, noise, and
interference feels that something is missing in his education. The new engineer
has a very difficult time ordering, specifying, or using hardware correctly.
Facilities and power distribution are a mystery. Surprisingly, all these areas
are accessible once the correct viewpoint is taken. This book has been written
to provide a better introduction to the field of electronics so that the parts that
are often omitted can be put into perspective.
The book uses very little mathematics. It helps to have some background in
electronics, but it is not necessary. The beginning student may need some help
from an instructor to fill in some of the blanks. The practicing engineer will
be able to read this book with ease.
Field phenomena are often felt to be the domain of the physicist. In a
sense this is correct. Unfortunately, without a field-based understanding,
many electronic processes must remain mysteries. It is not necessary to solve
difficult problems to have an appreciation of how things work. It is only necessary
to appreciate the fundamentals and understand the true nature of the
world.

http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471222909,subjectCd-PHA0.html

 

and there are a few good books that easily allow you to understand just how important a field based view of circuit analysis is.
http://onlinelibrary.wiley.com/doi/10.1002/0471433934.fmatter/pdf


http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471222909,subjectCd-PHA0.html

Hi,

The real difference is conservative vs non conservative. Conservative fields follow simpler rules so we dont have to know what the field is doing. Non conservative fields void some simple circuit analysis rules like Kirchoff's but otherwise we dont need the field data.

 

Hi,

The real difference is conservative vs non conservative. Conservative fields follow simpler rules so we dont have to know what the field is doing. Non conservative fields void some simple circuit analysis rules like Kirchoff's but otherwise we dont need the field data.

Sure but understanding the very common non-conservative forces like friction on different paths (or the electrical equivalent of changing fields causing path dependency) is essential in understanding real world interactions. Circuit analysis rules have their domain but as you say they don't provide insight into every sometimes simple problem.
Goto 48:00 this video for a demo

Detailed examination.

From a comment:

Kirchhoff assumes that the E field is irrotational, curl(E) =0. But Faraday's Law says that curl(E) =-dB/dt, so the E field is not conservative and the potential difference must be path dependent.

You're right, we don't need the field data, we need the field view as part of the total circuit mental image. Every time we look at an electromagnetic device like generators, electrical motors, speakers, microphones, video displays and just about anything that actually interacts with a world external to the circuits we use changing fields that violate Kirchhoff's Loop Rule. We don't need to calculate using field equations, we just need to think in a physically consistent framework.