basic ac theory question

[Jerry]

If electron flow with alternating current keeps changing direction, then it seems that current doesn't move along a path from one point to another, but instead moves back and forth. Yet AC wiring books describe current as moving from the hot/black side, through the load, and returning via the neutral/white side.

How does AC move along a path when the direction of current keeps changing?
Thanks for any insights,
Jerry

 

[Eeyore]

If electron flow with alternating current keeps changing direction,
then it seems that current doesn't move along a path from one point to
another, but instead moves back and forth. Yet AC wiring books
describe current as moving from the hot/black side, through the load,
and returning via the neutral/white side. How does AC move along a
path when the direction of current keeps changing ?

It's a simplification for convenience that's all.

Please don't post in html btw.

Graham

 

[John O'Flaherty]

If electron flow with alternating current keeps changing direction, then it seems that current >doesn't move along a path from one point to another, but instead moves back and forth. Yet >AC wiring books describe current as moving from the hot/black side, through the load, and >returning via the neutral/white side.

How does AC move along a path when the direction of current keeps changing?

The current moves to and fro, and does its work. A light bulb, for
example, gets just as hot when the current is going right-to-left as
when it goes the other way. No net movement of electrons is necessary.
Then why call the wires different names? To keep track of which wires
have voltage with respect to each other. At any instant in time,
whether they are plus or minus with respect to the other kind of wire,
two hot wires will have no voltage between them, and the same is true
of two neutral wires. Also, the neutral is connected to ground
somewhere, and its important for safety reasons to know which wire has
little or no voltage with respect to ground.

 

[Jerry]

Simplification makes sense but doesn't answer the question. Does AC move
along a path or just "back and forth"?

 

[Skeptic]

Think of sound. The air molecules move back and forth but do not travel from the source to the listener. Yet we still think of the sound traveling from one point to another. Don't confuse the wave with the medium. Waves move though the medium doesn't.


If electron flow with alternating current keeps changing direction, then it seems that current doesn't move along a path from one point to another, but instead moves back and forth. Yet AC wiring books describe current as moving from the hot/black side, through the load, and returning via the neutral/white side.

How does AC move along a path when the direction of current keeps changing?
Thanks for any insights,
Jerry

 

[John Popelish]

If electron flow with alternating current keeps changing direction,

That they do.

then it seems that current doesn't move along a path from
one point to another,
but instead moves back and forth.

Current isn't the movement of any electron, but the net
movement of charge through the conductor, at any point.
While an electron is going one way (and moving a tiny
fraction of an inch) the current it is part of is moving in
that direction, from the power generator to your house.
when that electron turns around, the current anywhere along
that path from generator to house goes the other way. This
is because the distance from the generator to your house is
a small part of a wavelength at that low frequency.

When you raise the frequency to the signals arriving through
the cable television system, this assumption of uniformity
direction all along the path, is no longer valid.

Yet AC wiring books describe current as moving
from the hot/black side,
through the load, and returning
via the neutral/white side.

Then they are mistaken.

The distinction between hot and neutral is that the
potential (voltage, not current) on the neutral wire with
respect to Earth is low (they are connected together at the
power panel and at the transformer on the pole). The
voltage between the hot conductor and Earth is much higher.
So connecting a load between hot and ground is quite
similar to connecting it between hot and neutral. If you
are standing on a dirt in your bare feet and you touch the
hot wire, you will understand why they chose this word to
describe that side of the circuit.

 

[John Fields]

Simplification makes sense but doesn't answer the question. Does AC move
along a path or just "back and forth"?

 

[Daniel Mandic]

How does AC move along a path when the direction of current keeps
changing? Thanks for any insights,
Jerry

It shakes, with a small head on that direction, where all the flow
begun.


Best Regards,

Daniel Mandic

 

[Alan B]

If electron flow with alternating current keeps changing direction,

then it seems that current doesn't move along a path from one point to
another, but instead moves back and forth. Yet AC wiring books describe
current as moving from the hot/black side, through the load, and returning
via the neutral/white side.
First of all, you mistake electron flow for charge flow. Current is not
electron flow, rather it is charge flow. One amp is defined as one Coulomb
of charge per second passing a given point.

Second, about your confusion: the books you talk about are making a
simplistic description of the connections being made in a circuit. The
supply side and the return side are necessary labels, helpful when building
or maintaining circuits.

How does AC move along a path when the direction of current keeps changing?
Thanks for any insights,

If there is no path, charge cannot move at all. So if charge is moving,
there must be a path. Think of a million hikers on a single-file trail.
The path is there, and the hikers are there, but they cannot decide which
way to go, so they sway back and forth. The ends of the trail show the
movement of the individual hikers within the trail; the energy of their
movement goes back and forth, and is noticeable.

 

[Tom Biasi]

.. Think of a million hikers on a single-file trail.

The path is there, and the hikers are there, but they cannot decide which
way to go, so they sway back and forth. The ends of the trail show the
movement of the individual hikers within the trail; the energy of their
movement goes back and forth, and is noticeable.

Sounds like a lot of fun, do they sing Koom-ba-ya?

 

[Wayne]

On Sun, 08 Oct 2006 12:41:13 GMT, in message
<[email protected]>, "Jerry" <nobody@no_where.com>
scribed:

First of all, you mistake electron flow for charge flow. Current is not
electron flow, rather it is charge flow. One amp is defined as one Coulomb
of charge per second passing a given point.

I have always understood charge as the flow of electrons if it is a
metal conductor. If it is not a metal conductor then charge is not
necessarily electrons.

 

[Puckdropper]

I'm sorry, did you say something?

Puckdropper

 

[jasen]

If electron flow with alternating current keeps changing direction, then
it seems that current doesn't move along a path from one point to
another, but instead moves back and forth. Yet AC wiring books describe
current as moving from the hot/black side, through the load, and
returning via the neutral/white side.

How does AC move along a path when the direction of current keeps
changing?

a similar question is

how do wheels travel when they just go round in circles?


the answer to your question could be that it travels like a wave with an
extremely long wavelength, but that could confuse more than it enlightens.

Bye.
Jasen

 

[Alan B]

I have always understood charge as the flow of electrons if it is a
metal conductor. If it is not a metal conductor then charge is not
necessarily electrons.

Charge is the energy produced when electrons move. A potential is
introduced at either end of the circuit path, which imparts energy to the
electrons in the conductors, causing them to move, which in turn creates a
net flow of charge. Charge has no mass and moves fast, close to c.
Electrons have mass, and move rather slow when excited. I wonder what
fundamental element moves in a non-metal conductor? Neutrons?

OK, best to leave the non-instructive, derisive satire to Phil Allison.
Er, except he's too dull for satire. Ah well, sorry. Charge does not flow
easily in non-metals (insulators) because elementally, they have few free
electrons, which means it is difficult to jostle them loose with potential
energy. Thus, you can apply voltage to a ceramic, or glass, and its
electrons will not budge, hence no charge will be produced.

Now, if you're talking about hole flow in a semiconductor, that's a whole
new bucket of worms; are you sure you want to go there?

 

[Alan B]

. Think of a million hikers on a single-file trail.

Sounds like a lot of fun, do they sing Koom-ba-ya?

Heh. Explaining things that cannot be directly observed is a dicey
enterprise!

 

[Fin]

I'm sorry, did you say something?

Puckdropper

yes, you're sorry.

 

[Tom Biasi]

On Sun, 8 Oct 2006 16:40:40 -0400, in message


Heh. Explaining things that cannot be directly observed is a dicey
enterprise!

I know, I was just having some fun. It really wasn't a bad example;
pretty good actually.

Tom

 

[Michael A. Terrell]

Then they are mistaken.

Those wiring books are describing the physical path of a circuit in a
way people who know nothing about electricity can wrap their heads
around. They don't need to know if it is AC or DC, worry about phase or
anything else. They just need to know how to hook up and outlet or a
light and switch. Some electricians don't know any more than that, yet
they can do good work that passes inspections.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Stanislaw Flatto]

If electron flow with alternating current keeps changing direction,
then it seems that current doesn't move along a path from one point to
another, but instead moves back and forth. Yet AC wiring books describe
current as moving from the hot/black side, through the load, and
returning via the neutral/white side.

They don't tell you the whole story, (I don't know who wrote this!). AC
as my teacher told me is a sinusoidal effect consisting of "positive"
(whatever it means) and "negative" half-waves. So what is "hot" and
"neutral" changes every half-cycle. Consider a steam engine piston,
moving forth AND back and yet doing "work".

How does AC move along a path when the direction of current keeps changing?

See above.

Thanks for any insights,
Jerry

HTH

Stanislaw

 

[jasen]

Charge is the energy produced when electrons move.

energy is not produced when electrons move
charge is a a number of electrons (or equivalent)

A potential is introduced at either end of the circuit path, which
imparts energy to the electrons in the conductors,

Nope. The potential exerts force on the electrons.

causing them to move, which in turn creates a net flow of charge.
Charge has no mass and moves fast, close to c.

electrons have mass... potential has no mass, and propogates (like a wave) at
speeds upto c.

Electrons have mass, and move rather slow when excited. I wonder what
fundamental element moves in a non-metal conductor? Neutrons?

electrons (in most cases) or ions (in ionic fluids) or holes
(in p-type semiconductors), neutrons may move but they carry no charge.

Charge does not flow easily in non-metals (insulators) because elementally,
they have few free electrons, which means it is difficult to jostle them
loose with potential energy.

potential energy doesn't jostle, (but heat does), potential actually exerts
no force,

however a difference in potential that creats the force proportional
to the difference in potential and inversely proportional to the distance.

Thus, you can apply voltage to a ceramic, or glass, and its
electrons will not budge,
yup.

hence no charge will be produced.

huh?

Bye.
Jasen