How electric circuits really work

[bobkolker]

I've been studying circuits, but I can't find any resources that really answer my specific questions. So far I understand that a battery creates a potential difference between the two terminals, one of which is positive while the other is negative. There is a buildup of positive charge on the positive side and buildup on the negative side, and this creates an electric field which can accelerate electrons from a location of high potential to one of low potential. When you connect a conducting wire between positive and negative terminals, this creates a path of least resistance which electrons can flow through, where the electrons are accelerated by the electric field that the battery creates. Hopefully all of this correct so far. My main question arises when it comes to voltage drops. What really is a voltage drop? If we connect one resistor to the circuit, a circuit with 12 V, then there must be a voltage drop across the resistor of 12 V. However, why is this the case? And also, how are the electrons still able to move if on the other side of the resistor there is 0 V, since there is a voltage drop?

I know that most of this is probably wrong, so I need someone to really help me understand how circuits and specifically voltage drops work.

Here is a "must read" Please read http://science.uniserve.edu.au/school/curric/stage6/phys/stw2002/sefton.pdf

Sefton demolishes the "garden hose" analogy and shows power is transmitted as a field effect. The electric and magnetic fields produce the Poynting Vector field which is really what carries the power from the energy source to the resistance.

See also http://cq-cq.eu/Galili_Goihbarg.pdf and http://amasci.com/elect/poynt/poynt.html

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

http://www.furryelephant.com/conten...tric-current/surface-charges-poynting-vector/

 

[sophiecentaur]

In doing the work, the electrons increase their kinetic energy,

That is a very weak model / analogy. The total mass of free electrons will be in the order of 1/(tens of thousands) of the mass of the conductor and their mean drift speed is around 1mms^-1. How much KE is that?
Your argument is a bit like explaining how a bicycle chain works by saying its KE is the main part of the energy it transfers to the wheels.

 

[Stephen Tashi]

There is a buildup of positive charge on the positive side and buildup on the negative side, and this creates an electric field which can accelerate electrons from a location of high potential to one of low potential.

There are "levels" of understanding physical phenomena. If you want to understand an electric circuit at the level of atomic physics then you have quite a job ahead of you. Even if you take the model of a electron as a small charged classical mass, the detailed physics of an electrical circuit is not simple. For example, if the electric field accelerating electrons was the only force on an electron then it should accelerate while in the wire and have greater velocity at the "downstream" end of the wire than at the upstream end of the wire.

You should seek a level of understanding that matches what you want to do. If you want to build everyday electric circuits then you don't need to understand what's going on at the atomic level - and maybe nobody really understands the atomic level. If you want to design vacuum tubes, or design radio antennas, you need a different level of understanding.

 

[sophiecentaur]

The way that 'modern' Science education goes doesn't help at all with this. For some reason, the curriculum seems to want students to 'explain' in their heads, every electrical phenomenon in terms a very badly defined 'electrons'.
Particles Rule and Confusion Reigns. Bring back Charge and Current and leave it at that until students have an actual clue what sub atomic particles are like. (But I have been harping on about this ever since forums were available on the Internet - and even before.)

 

[bobkolker]

The way that 'modern' Science education goes doesn't help at all with this. For some reason, the curriculum seems to want students to 'explain' in their heads, every electrical phenomenon in terms a very badly defined 'electrons'.
Particles Rule and Confusion Reigns. Bring back Charge and Current and leave it at that until students have an actual clue what sub atomic particles are like. (But I have been harping on about this ever since forums were available on the Internet - and even before.)

lots of charged particles moving in a stream IS a current.

 

[bobkolker]

There are "levels" of understanding physical phenomena. If you want to understand an electric circuit at the level of atomic physics then you have quite a job ahead of you. Even if you take the model of a electron as a small charged classical mass, the detailed physics of an electrical circuit is not simple. For example, if the electric field accelerating electrons was the only force on an electron then it should accelerate while in the wire and have greater velocity at the "downstream" end of the wire than at the upstream end of the wire.

You should seek a level of understanding that matches what you want to do. If you want to build everyday electric circuits then you don't need to understand what's going on at the atomic level - and maybe nobody really understands the atomic level. If you want to design vacuum tubes, or design radio antennas, you need a different level of understanding.

The easiest way I have found to understand energy flow in an electric circuit is by means of Poynting vectors. The electron move in the wire (slowly) because of potential difference. The electrons have the field E and the motion produces the magnetic field S. The Poynting vector E x S tells you the magnitude of the energy flow and the direction. BTW the energy flows from the battery to the resistance through -space-., not just along the wire. The "garden hose" model of energy flow in a circuit is all wrong. Think about it. When you switch on a light it lights up nearly instantly. If one had to wait for electrons to travel to the lightbulb from the battery it would take hours.

 

[sophiecentaur]

lots of charged particles moving in a stream IS a current.

Of course it is but how does that help when you are considering the right component to use in an electric circuit. And what is the nature of these charged particles that you are using in your model?
People forget that ALL the basics of Electrical Engineering were established long before the electron had been discovered. It is a deluded idea that electrons actually help in elementary electrical theory. I speak from experience. At School, we were not encouraged to bring electrons into our electrical basics until we knew enough about them to make valid connections. It was a massive help for me because I didn't waste time with half arsed analogies, which is all you can get from the electrons that kids are told about in School these days.