How do we explain powering a load without converting any current?

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nsaspook

Joined Aug 27, 2009
10,671
It's important for them to know that the electrical energy doesn't flow like mechanical pressure waves through the water, but in an electric transmission line the energy flows as fields in the space surrounding the wires. This doesn't mean the person needs to understand Maxwell, they just need to know these things called fields exist (in the physical sense) in the very beginning IMO.

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

kraus_poynt.gif
page 417, Fig 10-19, found in:
ELECTROMAGNETICS 2nd Ed., John D. Kraus & Keither R. Carver, McGraw-Hill 1973
This one above is interesting, because it shows one place where poynting vector energy flow is a crucial idea: Antenna Design! Kraus' Electromagnetics is essentially an antenna design book aimed at physics students. (But note that Kraus makes an important point: the source in the above diagrams ...is a battery! The propagating EM flow has 0Hz frequency.)
 

Ya’akov

Joined Jan 27, 2019
6,853
It's important for them to know that the electrical energy doesn't flow like mechanical pressure waves through the water, but in an electric transmission line the energy flows as fields in the space surrounding the wires. This doesn't mean the person needs to understand Maxwell, they just need to know these things called fields exist (in the physical sense) in the very beginning IMO.

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

View attachment 242614
I wish there was a convenient fluid analogy to capture the relationships of current and voltage to E and B fields.
 

nsaspook

Joined Aug 27, 2009
10,671
I wish there was a convenient fluid analogy to capture the relationships of current and voltage to E and B fields.
It's not necessary IMO. Fields are intuitive when taught properly.
https://onlinelibrary.wiley.com/doi/pdf/10.1002/0471433934.fmatter
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.
To illustrate the problem, consider an electric field that is constant everywhere.
Place a conducting loop of wire at some crazy angle in this field and ask a
question: What is the shape of the new field? This is a very difficult problem
even with a great deal of computing power. Now, have the field change sinusoidally and consider current flow and skin effect and the problem really gets
difficult. The ideas are important, but the exact answer is not worth worrying
about. Connecting wires and components to form circuits is standard practice. These conductors modify the fields around them. This is the same nasty
problem, and again it does not need an exact solution. What is needed is an
understanding of what actually takes place. Circuit theory does not consider
this type of problem.
The main problem IMO is that we wait to start with a math based (fields are just a mathematical construct) explanation when it should have been a physical explanation (fields exist just like matter) in the beginning of the electrical training.
 

Thread Starter

Mark Flint

Joined Jun 11, 2017
136
You seem to be trying to read more into it than there is.
When I ask questions I often show my ignorance but I just like getting to the bottom of things and I still have a long way to go in my understanding, so I ask anyway. But certainly I do like mysteries :)
 

Thread Starter

Mark Flint

Joined Jun 11, 2017
136
It's not necessary IMO. Fields are intuitive when taught properly..
Is there a water analogy to the phenomenon of a magnetic field being propagated every time a current shows up in a conductor? Isn’t the magnetic field a store of energy commensurate to the current in the wire, particularly coils of wire?
 

Ya’akov

Joined Jan 27, 2019
6,853
It's not necessary IMO. Fields are intuitive when taught properly.
https://onlinelibrary.wiley.com/doi/pdf/10.1002/0471433934.fmatter

The main problem IMO is that we wait to start with a math based (fields are just a mathematical construct) explanation when it should have been a physical explanation (fields exist just like matter) in the beginning of the electrical training.
When I ask questions I often show my ignorance but I just like getting to the bottom of things and I still have a long way to go in my understanding, so I ask anyway. But certainly I do like mysteries :)
I used to like mysteries in this way, but I came to realize that it was the question that was the mystery not the thing itself.

It's like digging a hole and then asking why it is there.

I know it's not clear at the time, but what I learned is that if something seemed very mysterious to me and not to people I could reasonably expect to be experts the mystery was a phantom and what I needed was to double down on understanding the explanation, not questioning its parts narrowly.

Things rarely survive a reductionistic analysis.
 

nsaspook

Joined Aug 27, 2009
10,671
Is there a water analogy to the phenomenon of a magnetic field being propagated every time a current shows up in a conductor? Isn’t the magnetic field a store of energy commensurate to the current in the wire, particularly coils of wire?
There are no good ones. Faith is required in the beginning with large thick lumps of rote learning before you 'learn' facts. We can try to use water based inductor analogies but IMO they simply waste time and effort better spent adsorbing sufficient electrical base knowledge to understand electrical concepts as unique properties in the universe.
 

MisterBill2

Joined Jan 23, 2018
13,704
Take a simple circuits like a 12v battery and a 5 amp filament bulb.

If we place meters before the bulb and after the bulb we see that current is 5 amps on both the positive and negative sides, while the voltage drops to a few millivolts.

Are we not taught that our electrical power is converted to light and heat in a light bulb? But if the current on the negative side of the circuit is identical to that on the positive side, what exactly was converted to light and heat?

If power = volts x amps and no amps were converted does that mean the bulb was powered completely by voltage alone? If not - what else is powering the bulb?

Thanks.
GIVEN THAT NO electricity escaped from the bulb, of course the amps exiting equal the amps entering. That is how it works. It can not work any other way!
AND NO!!!, we are not taught that electrical power is magicly converted. The power does some work producing the light. So you need to read the rest of the secction on electrical power. Once you understand that the explanation will be obvious to you. (for a hint, consider that there is a voltage of 12 volts across that bulb.) That 12 volts times the 5 amps equals the 60 watts delivered.
 

BobaMosfet

Joined Jul 1, 2009
2,053
If an electron is just a negative charge what does it donate to the reaction, and so what has changed with it (if anything) after that reaction?
It's not the electron, it's the movement of that electron and the friction it causes, leading a thermochemical reaction.
 

Thread Starter

Mark Flint

Joined Jun 11, 2017
136
GIVEN THAT NO electricity escaped from the bulb, of course the amps exiting equal the amps entering. That is how it works. It can not work any other way!
AND NO!!!, we are not taught that electrical power is magicly converted. The power does some work producing the light. So you need to read the rest of the secction on electrical power. Once you understand that the explanation will be obvious to you. (for a hint, consider that there is a voltage of 12 volts across that bulb.) That 12 volts times the 5 amps equals the 60 watts delivered.
We have current going through the bulb and a voltage drop across the bulb, and the battery discharges at the rate of current flow. No current is consumed or converted in the bulb and the battery discharges as the separation of charges on the plates is diminished by effectively shunting the battery terminals through the load. As charge separation diminishes the potential difference drops between the plates and the battery needs charging again to force charge separation. Or do you see it another way?
 

MisterBill2

Joined Jan 23, 2018
13,704
The current passing through the bulb does work, and thus energy is delivered. The phuics of it is fairly simple. And yes, the battery will need to be recharged.
I am not sure what point the TS is making here.
I suggest continued studies of electrical power and circuit fundamentals rather than challenging reality. Even the math is not that complicated. A lack of understanding should lead to additional study, not an argument.
 

Thread Starter

Mark Flint

Joined Jun 11, 2017
136
I used to like mysteries in this way, but I came to realize that it was the question that was the mystery not the thing itself.
I can see how trying to wrap our brains around theoretical matters can lead to this scenario. If a scientific theory is the attempt to explain observable phenomenon then it should take into account all the observations, and I agree with your last statement but in the sense that electromagnetics in general seem often reduced to simplistic incomplete analogies. So, if I short the terminals of a 12v battery I will get light and heat in lots of quantities as opposite charges on the plates come into equilibrium very quickly and the battery discharges. If I put a resistance such as a light bulb in the path then this reaction slows down. But what else actually changes? Current passes from one plate polarity to the other "un diluted" by the load, and at the point of reaching the opposite plate the charges must cancel. Does this cancellation of charges not have a bearing on how energy in the battery is dissipated, used up, consumed, converted, etc?
 

Ya’akov

Joined Jan 27, 2019
6,853
I can see how trying to wrap our brains around theoretical matters can lead to this scenario. If a scientific theory is the attempt to explain observable phenomenon then it should take into account all the observations, and I agree with your last statement but in the sense that electromagnetics in general seem often reduced to simplistic incomplete analogies. So, if I short the terminals of a 12v battery I will get light and heat in lots of quantities as opposite charges on the plates come into equilibrium very quickly and the battery discharges. If I put a resistance such as a light bulb in the path then this reaction slows down. But what else actually changes? Current passes from one plate polarity to the other "un diluted" by the load, and at the point of reaching the opposite plate the charges must cancel. Does this cancellation of charges not have a bearing on how energy in the battery is dissipated, used up, consumed, converted, etc?
If you have a spring motor and wind it up, and use a rubber belt drive to power a fan with it, why does the belt get used up? Isn't it converted into "wind" by the fan? How can there be the same amount of belt before and after the fan drive pulley? It's very mysterious.
 

Ya’akov

Joined Jan 27, 2019
6,853
Even a cursory reading of the history of science would warn against this, wouldn't you agree?
No. You are not a researcher. Are you investigating the possibility that your gap in understanding represents a gap in the incredibly successful theories that bring us amazing practical technologies? No, you aren't. If you were going to spend your time trying to build on the theories, and found yourself unable to make progress because of something that appeared to be a gap in the current understanding, then spending your time trying to concoct apologetics for it because of "faith" would be something warned against by the history of science.

But, if, as you are, a person just confused by something that is a phantom created by your own gaps in knowledge, the right course, also prescribed by an understanding of the history of science, is to set aside this question as you pursue further understanding of what current theory says.

If, after you understand how all the relevant pieces of the theory work together and you still have this question, they who knows, maybe you've stumbled on something that many brilliant people have missed to this point. This seems exceedingly unlikely.
 

Thread Starter

Mark Flint

Joined Jun 11, 2017
136
If you have a spring motor and wind it up, and use a rubber belt drive to power a fan with it, why does the belt get used up? Isn't it converted into "wind" by the fan? How can there be the same amount of belt before and after the fan drive pulley? It's very mysterious.
There is the same amount of belt like there is the same amount of current before and after the load.
 

Ya’akov

Joined Jan 27, 2019
6,853
There is the same amount of belt like there is the same amount of current before and after the load.
Yes and there is no mystery to it. We don't ask why the belt isn't used up in converting the energy we put into the spring motor by winding it into the motion of the air and the heat of friction. You'd have to think the belt is something turned into those things to expect it to be diminished on the far side of the pulley.
 

ericgibbs

Joined Jan 29, 2010
16,752
hi Mark,
Read this battery link.
Your understanding of voltage potential and current flow is way off mark.
The Electrons don't get used up or changed in any way, its a chemical disassociation and recombination process within the battery.
ie: electron movement from one plate to another plate within the battery via the electrolyte.
E
https://web.mst.edu/~gbert/BATTERY/battery.html
 

nsaspook

Joined Aug 27, 2009
10,671
There is the same amount of belt like there is the same amount of current before and after the load.
I said you need faith in the beginning. This is why I normally tell people to forget about electrons and physical current when struggling with circuit concepts. Trying to deal with microscopic EM details too early leads to a rathole filled with jumbled ideas. There will be a turning point were the lumps of information, taken a face value, will click together so you can see the total EM energy transportation picture in rough. There is still an endless pit ahead but now you will have to tools to sort ideas into nice ordered bins. The fact you are asking these questions means you already see the limitations of strict circuit theory but currently don't have the knowledge to see the system picture yet.

https://ecee.colorado.edu/~ecen3400/Textbook/Chapter 2 - Circuit theory and EM.pdf
 
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