elelctric waves

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stjohnbarleycorn

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I am trying to get a better handle on current flow, and just read some info on waves
What I got out of it ( and maybe I got it wrong) is that you have you electrons in the wire with their own energy, and by introducing a power source this created a "wave" that flows down the conductor using the wire and electrons to pass energy down the wire. I understand the electrons move slowly in the wire and its the energy that moves not the electrons per se. So I am now thinking that the electromagnetic wave is what is really going on, and that is what you read with your amp clamp. Is this also connected with the energy moving on the outside of the wire?
Any ideas would be appreciated, or web sites that can explain this subject. thanks.
 
stjohnbarleycorn said:
I understand the electrons move slowly in the wire and its the energy that moves not the electrons per se.
Click to expand...
Electrons have energy. Not a lot (1.6*10^-19 J) but then there are an awful lot of them.
My physics teacher had what I thought then to be a fairly good analogy for current flow.
A piece of copper wire has free electrons. Imagine it like a railway tunnel filled with wagons. Push another wagon in at one end an another pops out at the other end. They don't have to move very fast to get a quick result.
 
Besoeker said:
Electrons have energy. Not a lot (1.6*10^-19 J) but then there are an awful lot of them.
My physics teacher had what I thought then to be a fairly good analogy for current flow.
A piece of copper wire has free electrons. Imagine it like a railway tunnel filled with wagons. Push another wagon in at one end an another pops out at the other end. They don't have to move very fast to get a quick result.
Click to expand...

I always use the billards balls analogy, but about the same thing. You can explain a lot of physics stuff with a pool table.
 
thanks, what I use is one of the things with the 6 ball bearings on stings hanging from a hanger, when you let go one it hits the others and the end one swings up and comes back like AC. LIke billard balls.

Now after reading the wave thing I was trying ( more for myself) to understand that its not like that, its more like an energy filed that is pushing through around the electrons, causing the energy in the electrons to pass from one to another.
 
energy wave

energy wave

If you were able to line up a hundred billiard balls, the not visible energy wave from one through ninety-nine would give one an idea of the collision and energy exchange.
 
electrons are matter, not energy wave

electrons are matter, not energy wave

Sorry, I actually was busy for a few days...

The billiard balls represent the electrons. The magnetic energy wave is the invisible energy wave phenomenon through the line of balls.
 
so to demonstrate the action you would need to use ball bearings and a magnet to move the energy down the line, instead of hitting one ball at the end and seeing the last ball move?
 
not sure

not sure

...not sure how to demonstrate a magnetic wave using magnets and ball-bearings.

Once, I told a group that the wave in the conductors was sort-of like sound waves. I was able to send my voice across the room at 600 or so miles per hour without causing violent, hurricane force winds. The sound wave is projected by my voicebox and carried through the still air to the receiving person's eardrum.

It is magical...
 
Here's a Link to a lot of information on the physic's of things, it might not answer all your direct questions but it will tie together some of the principles that your dealing with, enjoy. (touch and go into any of the ovals)

Hyperphysics
 
stjohnbarleycorn said:
yes but is it the energy wave that makes the electrons move or is it the electrons moving that creates the wave?
Click to expand...
The wave is produced by the energy applied (AC). It is the physical relationship of the magnetic field to the coil under its influence. As the rotor rotates thorugh 360 deg. the sine wave is produced. When applied to a conductor, the electrons react to the variation in this energy (voltage) and produces a copy of the energy wave (current) in a closed circuit.
 
richxtlc said:
The wave is produced by the energy applied (AC). It is the physical relationship of the magnetic field to the coil under its influence. As the rotor rotates thorugh 360 deg. the sine wave is produced. When applied to a conductor, the electrons react to the variation in this energy (voltage) and produces a copy of the energy wave (current) in a closed circuit.
Click to expand...

Ok thanks. I had envisioned it as the electrons moving from one atom to the other, down the line so to speak. Over time electrons do move at a certain speed. The forces in the atoms/electron exchange delivers the energy at the load.
But now I am thinking that it is the electromagnetic wave that flows on the outside of the conductor, that causes the electron movement within the conductor. ANd its the electromagnetic wave that is causing the work to be done in the load.

does that make sense?
 
Here is a simplified, but reasonably accurate description of what happens with electrons and electric fields. I say simplified because electromagnetic field theory has many "complications", describing which is the topic of many books.

It may be easier to start thinking about DC. If you look at a small enough time interval, AC looks like DC as the potential changes very little during that period of time, and can be considered as constant. The voltage source sets up an electric field in the wire by putting the opposite ends of the wire at different electric potentials (actually, the field is everywhere - it is just the conductor where the most interesting things happen). Voltage is the measure of the potential. The application of the potential can happen through various methods (magnetic, mechanical, or chemical), but isn't really what is important here - just that there is a potential difference applied.

This electric field created by the difference in potential exerts a force on the electrons, pulling them one way or the other. In some materials there are many "free" electrons that can move easily in large numbers ("conductors", like in copper wire), and in other materials there are few "free" electrons, and they are much more difficult to move in large numbers ("insulators", like most plastics and air). Electrons have a "charge" (which is actually what the electric field is applying the force on), and as charge moves, it is called "current". If there is a good conducting path from the area of high potential to low potential, the electrons, and hence charge, will move easily, creating current.

Now consider AC. What is happening is that the potential across the conductor is changing over time, so that at one point in time one end has a high potential and the other has a low potential, and later, they have switched so that the previously low potential end becomes high potential, and the previously high potential end becomes low potential. This causes the electrons to first move in one direction, and then to stop, and then move the other direction as the electric field changes direction. The actual distance the electrons travel in the conductor depends on the potential, how many electrons are available to move, how easily they move in the conductor, and the frequency with which the AC changes direction (the slower the change, the farther they go). With AC and typical lengths of conductors, it is unlikely that an electron from one end ever makes it all the way to the other end. But with DC or very short conductors, it is possible that electrons may travel all the way from one end to the other.

Another aspect is that when charge moves (current), it creates a magnetic field. It is basically this magnetic field that is measured by a clamp-on current meter. And prior to digital meters, it was actually this magnetic field that was used to measure both AC and DC currents and voltages (for voltage, a conducting path is provided so that current will flow in the meter). The magnetic field created by the current causes a force to be applied to a permanent magnet that is mounted on a needle, which generally prevented from moving by a spring. As the magnetic field increases due to an increase in current, it applies more force to the permanent magnet, pushing the needle against the force applied by the spring, causing it to move and display the current or voltage being measured.
 
learn every day

learn every day

My goal is to learn every day. So far it's holding...


When anyone refers to electrons travelling, I start to miss the understanding. I can see local collision and possible sharing, but after that I'm foggy on the movement of electrons.

Any good explanation would be appreciated.
 
SAC said:
This electric field created by the difference in potential exerts a force on the electrons, pulling them one way or the other. In some materials there are many "free" electrons that can move easily in large numbers ("conductors", like in copper wire), and in other materials there are few "free" electrons, and they are much more difficult to move in large numbers ("insulators", like most plastics and air). Electrons have a "charge" (which is actually what the electric field is applying the force on), and as charge moves, it is called "current". If there is a good conducting path from the area of high potential to low potential, the electrons, and hence charge, will move easily, creating current.

Now consider AC. What is happening is that the potential across the conductor is changing over time, so that at one point in time one end has a high potential and the other has a low potential, and later, they have switched so that the previously low potential end becomes high potential, and the previously high potential end becomes low potential. This causes the electrons to first move in one direction, and then to stop, and then move the other direction as the electric field changes direction. The actual distance the electrons travel in the conductor depends on the potential, how many electrons are available to move, how easily they move in the conductor, and the frequency with which the AC changes direction (the slower the change, the farther they go). With AC and typical lengths of conductors, it is unlikely that an electron from one end ever makes it all the way to the other end. But with DC or very short conductors, it is possible that electrons may travel all the way from one end to the other.
Click to expand...

The movement of electrons occurs in the outer shell of the atom. As stated above when sufficient potential (energy) is applied these atoms move from one outer shell to another. As they move they may bump into each other. When this happens they give off energy in the form or heat. The resistance of the wire (conductor) is determined by how many electrons an electron will hit on it journey thorugh the conductor. The more tightly spaced the atoms, the higher the resistance. Also, the more energy applies to these electron the more energetic they become and the greater the likelyhood that they will collide.
 
SegDog said:
My goal is to learn every day. So far it's holding...


When anyone refers to electrons travelling, I start to miss the understanding. I can see local collision and possible sharing, but after that I'm foggy on the movement of electrons.

Any good explanation would be appreciated.
Click to expand...
I don't know about good........you can be the judge of that.

Electrons have a charge measured in coulombs. (Actually, for each electron it is a very small fraction of a coulomb but then there are usually very large numbers of them)
One coulomb is one amp for one second. 1 As = 1 C
Or one amp is one coulomb per second. 1 A = 1 C/s

As electrons move along a wire, they take this charge (coulombs) with them.
The total charge depends on the number electrons moving.
The number (times the individual charge) that pass a given point in a second gives you current.

That's qualitative. Actual numbers of electrons gets a bit mind boggling and probably no help in basic understanding. But, for context....
One coulomb is the charge of about 6,250,000,000,000,000,000 electrons.
 
simple...

simple...

Thank you.

Just like the OP, I'm always seeking the best way to explain things to not only the uninitiated but, also, the advanced student.

When we talk about electrons flowing, it confuses the masses; rightly so. Throw in a few negative exponents and watch the eyes glaze over.
 
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