I always thought for a sine wave, you need a 2 "wires" and that the
flow of electricity changed depending on the analog values. In other words,
you need a positive & a negative. For example, a waveform "peak" would be
a speaker's cone moving outwards and back to 0, while a trough would be the
cone moving inwards & back to 0. Translating this to wires to mean that the
electrons flow from A-B while the voltage increases & goes back to 0 and vice
versa (for a trough, the electrons flow from B-A while voltage increases &
goes back to 0)

That's why I don't understand how RCA & mini-jacks work since
a) RCA...one wire connected to ground. Where is the signal coming from? Ground
doesn't generate the audio signal?

b) Common ground...how can that work, shouldn't there be four different
slivers on the mini-jack?

If someone could just explain how a sine wave works on RCA &
(stereo) mini-jacks, that would be very helpful. In other words, just point
out where the negative & positives are (as when you connect a speaker, you
need a negative & a positive).

"infamis" wrote ...
I always thought for a sine wave, you need a 2 "wires"

Any electrical circuit, whether it is carying AC (sine
waves, audio, mains power, etc.) or DC (like your car
battery) takes a complete circuit.

and that the flow of electricity changed depending on
the analog values.

So far, so good.

In other words, you need a positive & a negative.

You may be confusing yourself here. There is no
"positive" and "negative" in AC because it changes
several thousand times every second.

For example, a waveform "peak" would be a speaker's
cone moving outwards and back to 0, while a trough
would be the cone moving inwards & back to 0. Translating
this to wires to mean that the electrons flow from A-B
while the voltage increases & goes back to 0 and vice
versa (for a trough, the electrons flow from B-A while
voltage increases & goes back to 0)

That's why I don't understand how RCA & mini-jacks
work since
a) RCA...one wire connected to ground. Where is the
signal coming from? Ground doesn't generate the audio
signal?

The AC signal is carried on the inner pin of the RCA jack
and the ground provides the return path for the complete
circuit. Just as the body of your car carries the return path
for the battery power that runs the starter motor, the power
that runs your lights, and even the audio that goes to the
rear speakers, etc.

b) Common ground...how can that work, shouldn't there
be four different slivers on the mini-jack?

Yes, one method of carrying signal current uses a
BALANCED line where there are two wires, neither of
which are ground. As one side is going positive, the other
side is going an equal distance negative. This method is
typically used for microphones and professional audio
equipment. Because it is more expensive, consumer
electronic equipment tends to use UN-balanced kinds
of connections. Clearly this is quite workable in hundreds
of millions of cases around the planet.

If someone could just explain how a sine wave works
on RCA & (stereo) mini-jacks, that would be very
helpful. In other words, just point \out where the negative
& positives are (as when you connect a speaker, you
need a negative & a positive).

Typical consumer equipment uses UN-balanced connections.
Think of a kid on a pogo stick. The movement is all referenced
against ground. But the ground has to be there even if it
doesn't move. You can't use a pogo-stick in outer space.

Most professional equipment uses BALANCED connections.
Think of two kids on a see-saw (teeter-totter). When one
goes up, the other goes down (and alternating vice-versa.)

"infamis" wrote in message
om...
I always thought for a sine wave, you need a 2 "wires" and that the
flow of electricity changed depending on the analog values. In other
words,
you need a positive & a negative.

AC needs no more wires than DC. Two wires, to be specific, which we
normally call signal and ground.

Consider a light bulb powered by a battery. Two wires, one from battery +
to the light bulb, and the other from battery - to the other side of the
light bulb.

Now turn the battery backwards. Obviously, you still need only 2 wires, and
the light bulb still works, since the light bulb is not sensitive to
polarity.

Now replace that battery by an AC generator. You still need only two wires.
The sine wave generator acts like a battery that is switching back and forth
periodically.

Audio equipment designates one of the two wires "ground" because that is the
one that is shared by many different inputs and outputs. "Ground" is not an
electrical phenomenon; it just means something has been chosen to be the
common reference point.

The AC signal is carried on the inner pin of the RCA jack
and the ground provides the return path for the complete
circuit. Just as the body of your car carries the return path
for the battery power that runs the starter motor, the power
that runs your lights, and even the audio that goes to the
rear speakers, etc.

The inner pin is just one conductor, correct? Where's the other conductor at?
Is it ground? If that's so, that's what I'm not getting. If ground means
there's a rod stuck in the earth, how can that be generating the other "half"
of the AC signal?

Typical consumer equipment uses UN-balanced connections.
Think of a kid on a pogo stick. The movement is all referenced
against ground. But the ground has to be there even if it
doesn't move. You can't use a pogo-stick in outer space.

I take that to mean that there would be three conductors.
a) Our theoretical ground
b) The conductor which flows electrons left-right when the kid goes up.
c) The conductor which flows electrons left-right when the kid goes down.

But an audio signal is only 2. That would mean that either b) or c) is somehow
combined with a). How would the other device know how to separate the real
signal (b or c) from ground (a)?



My main thing is I don't see how a rod stuck in the ground can generate
the other "half" of the audio signal.

In article , "mc" wrote:
Now replace that battery by an AC generator. You still need only two wires.
The sine wave generator acts like a battery that is switching back and forth
periodically.

OK, I understand that....

Audio equipment designates one of the two wires "ground" because that is the
one that is shared by many different inputs and outputs. "Ground" is not an
electrical phenomenon; it just means something has been chosen to be the
common reference point.

But if you're throwing away one of the wires from the audio signal & replacing
it by a wire connected to the ground (the metal rod in the earth), how can
that metal rod be generating the rest of the signal. In DC, you have (+) and
(-). It seems to me that it's like throwing away the (-) away and replacing it
by, I don't know (X). That makes me wonder where the other half of the signal
is coming from.

"infamis" wrote ...
The AC signal is carried on the inner pin of the RCA jack
and the ground provides the return path for the complete
circuit. Just as the body of your car carries the return path
for the battery power that runs the starter motor, the power
that runs your lights, and even the audio that goes to the
rear speakers, etc.

The inner pin is just one conductor, correct? Where's the
other conductor at? Is it ground?

Yes, it most definitely is ground.

If that's so, that's what I'm not getting. If ground means there's
a rod stuck in the earth, how can that be generating the other
"half" of the AC signal?

Maybe you are confusing yourself by thinking that conductors
*generate* signals? They DO NOT generate signals, they only
*conduct* them (hence, the name ;-) . Whatever generated the
signal uses the conductors to get the voltage from the source
to the the destination.

Typical consumer equipment uses UN-balanced connections.
Think of a kid on a pogo stick. The movement is all referenced
against ground. But the ground has to be there even if it
doesn't move. You can't use a pogo-stick in outer space.

I take that to mean that there would be three conductors.
a) Our theoretical ground
b) The conductor which flows electrons left-right when the kid goes
up.
c) The conductor which flows electrons left-right when the kid goes
down.

The kid on the pogo-stick is feeling neglected. :-)

A circuit is a loop of wire that goes from the source, through
all the destinations, and back to the source. Your (b) and (c)
are the circuit [in a simplistic view]. It makes no difference
(for the purposes of your discussion) whether ONE of the points
in this circuit is grounded. Clearly, of TWO or more points
on this circuit are grounded, you have a dead short and no
signal.

Maybe it would be helpful to look up all the dictionary
definitions of "circuit" (besides the electrical one).

But an audio signal is only 2. That would mean that either b)
or c) is somehow combined with a).

Not "combined with". Connected to.

How would the other device know how to separate the real
signal (b or c) from ground (a)?

The signal is the difference between your (b) and (c) without
reference to any other point in the known universe. If you now
"ground" either (b) or (c), it makes no change to the differential
voltage between (b) and (c). The receiving device looks at
the difference between (b) and (c) and does not care if one
of them is connected to ground or not.

Your (b) and (c) exchange identities thousands of times
every second. Connecting either (b) or (c) to (a) ground
changes nothing.

Ground is not a signal. It is just a reference point.

My main thing is I don't see how a rod stuck in the ground
can generate the other "half" of the audio signal.

* Conductors DO NOT generate signals.
* Audio signals don't have "positive halves" and
"negative halves".
* It makes no difference to the circuit whether one
point is grounded or whether the entire circuit is
"floating" ("differential", "balanced").

In article , "Richard Crowley" wrote:
If that's so, that's what I'm not getting. If ground means there's
a rod stuck in the earth, how can that be generating the other
"half" of the AC signal?

Maybe you are confusing yourself by thinking that conductors
*generate* signals? They DO NOT generate signals, they only
*conduct* them (hence, the name ;-) . Whatever generated the
signal uses the conductors to get the voltage from the source
to the the destination.

I know that conductors don't generate signals, they're just the
transport...but...

A circuit is a loop of wire that goes from the source, through
all the destinations, and back to the source. Your (b) and (c)
are the circuit [in a simplistic view]. It makes no difference
(for the purposes of your discussion) whether ONE of the points
in this circuit is grounded. Clearly, of TWO or more points
on this circuit are grounded, you have a dead short and no
signal.

What does it really mean to be grounded? I guess I'm confused there. In all
the books I've read, grounded means it's connected to a metal rod stuck inside
the earth's crust. That makes me think that the circuit is:

audio_generating_source - conductor wire A - destination device - conductor
wire B - earth.

When I think it needs to be:

audio_generating_source - conductor wire A - destination device - conductor
wire B - audio_generating_source

Obviously you can't stick another metal rod in the earth & connect it back to
the audio_generating_source.

How would the other device know how to separate the real
signal (b or c) from ground (a)?

The signal is the difference between your (b) and (c) without
reference to any other point in the known universe. If you now
"ground" either (b) or (c), it makes no change to the differential
voltage between (b) and (c). The receiving device looks at
the difference between (b) and (c) and does not care if one
of them is connected to ground or not.

OK...are you saying that when (a) is +12V, if (b) was not connected to ground
it should be -12V. But if it is connected to ground, it may be -14V? That
means that ground was adding 2 volts? Or that the whole audio signal is offset
2 Volts above the X axis...like a DC correction?

* Conductors DO NOT generate signals.
Understand that.

* Audio signals don't have "positive halves" and
"negative halves".
Understand that, I guess I'm just not using the right words. There is no (+)
or (-) in AC since they change roles frequently.

* It makes no difference to the circuit whether one
point is grounded or whether the entire circuit is
"floating" ("differential", "balanced").

OK, they why ground? Maybe I just don't get the whole point of grounding if it
makes no difference on the audio signal once they are differenced against
each other.

"infamis" wrote in message
om...
The AC signal is carried on the inner pin of the RCA jack
and the ground provides the return path for the complete
circuit. Just as the body of your car carries the return path
for the battery power that runs the starter motor, the power
that runs your lights, and even the audio that goes to the
rear speakers, etc.

The inner pin is just one conductor, correct? Where's the other conductor
at?
Is it ground? If that's so, that's what I'm not getting. If ground means
there's a rod stuck in the earth, how can that be generating the other
"half"
of the AC signal?

Ground does not mean a rod stuck in the earth. Ground simply means common.

Let me explain the 3 meanings of ground in electronics.

(1) A rod stuck in the earth, either for lightning/high-voltage safety, or
to use the earth as part of an antenna system.

(2) The chassis of equipment. This is usually connected to (1) indirectly
through the power lines, but it need not be; the equipment works just as
well without doing that (e.g., portable, battery-operated equipment); we
usually tie (2) to (1) through the power line for high-voltage safety, to
better control what would happen if things inside got accidentally connected
to the case or chassis.

(3) A reference point in a circuit.

Consider an imaginary amplifier that consists of a 4-terminal black box.
The input signal goes to terminals A and B. The output signal is taken from
terminals C and D.

Suppose now that inside the amplifier, B and D are connected together. That
is in fact the way amplifiers are usually built.

In that case we will say B = D = ground. It need not be grounded in sense
(1) or (2), although in fact, for hum protection, it is usually connected to
ground in sense (2).

"Ground" merely means "shared by the input and the output."

Now... This amplifier still has 4 terminals (2 wires for input and 2 wires
for output) even though the input "ground" wire is connected to the output
"ground" wire.

Is this making things any clearer? The AC that comes in through an RCA plug
requires 2 conductors, which are the pin of the plug and the outer shield of
the plug. The AC that comes out to drive the next device also requires 2
conductors, the pin of its plug and the outer shield of its plug. It
happens that, the way amplifiers are built, the outer shields of the 2 plugs
are connected together and are considered "ground."

I should perhaps work through all this with batteries and light bulbs, but
it would require some diagrams.

"infamis" wrote in message
om...
In article , "mc"
wrote:
Now replace that battery by an AC generator. You still need only two
wires.
The sine wave generator acts like a battery that is switching back and
forth
periodically.

OK, I understand that....

Audio equipment designates one of the two wires "ground" because that is
the
one that is shared by many different inputs and outputs. "Ground" is not
an
electrical phenomenon; it just means something has been chosen to be the
common reference point.

But if you're throwing away one of the wires from the audio signal &
replacing
it by a wire connected to the ground (the metal rod in the earth), how can
that metal rod be generating the rest of the signal. In DC, you have (+)
and
(-). It seems to me that it's like throwing away the (-) away and
replacing it
by, I don't know (X). That makes me wonder where the other half of the
signal
is coming from.

Rods in the ground have nothing to do with it. "Ground" means something
entirely different here -- it means "the conductor that happens to be shared
by the input and the output." See previous message.

That makes me think that the circuit is:

audio_generating_source - conductor wire A - destination device -
conductor
wire B - earth.


Which it is not.

When I think it needs to be:

audio_generating_source - conductor wire A - destination device -
conductor
wire B - audio_generating_source


That's what it is, and conductor wire B is the outer shield of the cable,
which is called "ground."

That is an ordinary (not differential) signal. A differential signal would
use 2 wires neither of which is grounded in any of the senses of the world.

OK, they why ground? Maybe I just don't get the whole point of grounding
if it
makes no difference on the audio signal once they are differenced against
each other.

For the sake of shielding, we arrange it so that all of the inputs and
outputs of an amplifier have their outer shields connected together and to
the chassis of the amplifier. That keeps hum from being picked up. Every
AC connection still has two conductors (inner pin and outer shield).

For the sake of high-voltage safety, we arrange it so that the chassis of
the amplifier *may* also be connected to the earth through the power lines.
Not all amplifiers do this. Laboratory test equipment does.

That is the connection between the three senses of "ground" that I defined 2
messages back.

Audio systems do not have, or require, rods driven into the ground. Let go
of that concept. That is not what "ground" means with an audio signal. Let
go of that.

On Sat, 11 Feb 2006 18:36:48 GMT, (infamis)
wrote:

But if you're throwing away one of the wires from the audio signal & replacing
it by a wire connected to the ground (the metal rod in the earth), how can
that metal rod be generating the rest of the signal. In DC, you have (+) and
(-). It seems to me that it's like throwing away the (-) away and replacing it
by, I don't know (X). That makes me wonder where the other half of the signal
is coming from.

"Ground" is a reference point. It may or may not be linked to Earth.
What matters is that a wire has a voltage difference to it. If it
does, current will flow.

In an unbalanced audio connection, there generally ARE two wires. The
grounded one commonly acts as a screen as well as a voltage reference.

"infamis" wrote ...
What does it really mean to be grounded?

Depends on what you mean by "ground". See "mc"s posts
for several good descriptions of what the various meanings
of the word "ground" are.

I guess I'm confused there. In all the books I've read, grounded
means it's connected to a metal rod stuck inside the earth's crust.

You don't really believe that. Else you would be asking why
your RCA and mini-jacks didnt have a wire running to a ground
rod. And there you have two different meanings of the word
"ground": a) a connection "to the earth's crust", and b) a common
point of reference and shielding (i.e. most consumer electronic
equipment).

That makes me think that the circuit is:

audio_generating_source - conductor wire A - destination
device - conductor wire B

You seem to have a good grasp of what it takes to make a complete
"circuit". Did you look up the other dictionary definitions of the
word "circuit"?

- earth.

But you seem to repeatedly go wrong when you think that
"ground" has some sort of magical properties. In your circuit
above, any one point can be connected to ground without
changing the functionality of the circuit.


When I think it needs to be:

audio_generating_source - conductor wire A - destination
device - conductor wire B - audio_generating_source

Obviously you can't stick another metal rod in the earth
& connect it back to the audio_generating_source.

Sure you can. The "earth's crust" is a conductor just as a
piece of copper wire is. It is not quite as good as copper
wire, but megawatts of power are transmitted all over the
planet using the earth's crust as the return path of the circuit.

The power that runs the computer you are reading this on
is likely transmitted through the ground (on the return path
of the high-voltage side). When you see a single wire on
the power poles with taps going into the transformers, note
that the other side of the transformer is connected to a
ground wire. The electricity comes from the generator,
through the single wire along the poles, into the transformer
(the "destination"), and then returns through the earth's
crust back to the generator.

One of the meanings of "ground" is "the earth's crust".
And that "ground" is a *conductor*.

OK...are you saying that when (a) is +12V, if (b) was not
connected to ground it should be -12V. But if it is connected
to ground, it may be -14V?

No. When the signal is at "+12V", ALL the circuit is at +12V.
A few milliseconds later it might be -12V, and then ALL the
circuit will be -12V.

Furthermore, voltage doesn't exist in space. It cannot be
"measured" without some point of reference.

Your analogy is flawed, but if we accept it anyway, in your
scenario if (a) is +12 and (b) is -12, and then you grounded
(b) for example, (a) would be +24 and (b) would be zero.

That means that ground was adding 2 volts? Or that the
whole audio signal is offset 2 Volts above the X axis...
like a DC correction?

* Conductors DO NOT generate signals.
Understand that.

OK, so which is it? Do you *really* understand that
conductors do not generate signals, or do you believe
that connecting something to ground is "adding 2 volts"?
I don't know how to reply to you when even you don't
know what you believe (or not)?

OK, they why ground? Maybe I just don't get the whole
point of grounding if it makes no difference on the audio
signal once they are differenced against each other.

To answer that, you must be VERY SPECIFIC about what
you mean by "ground". Select one...

1) "ground" means the "crust of the earth"
2) "ground" means a common point of reference in an
electronic device, typically the metal chassis or case.

If you mean (1), then people ground things to...
a) to reduce interference through the air (as from a radio/
TV station).
b) to make potentially dangerous power safer. All mains
power in the civilized world is conected to ground at
one point for this reason.
c) to provide a safe path for lightning so that their electronic
stuff doesn't get zapped.

If you mean (2), then people ground things to...
a) to use a convienent return path for power and signals.
For example, the outside of your RCA jacks or mini-phone
plugs, etc. Or virtually everything in your car.
b) to provide a common reference point for various
pieces of equipment.
c) to "shield" things from interference, similar to (1)a)
above.

This is a very simplistic and even *******ized explanation
and can be blasted by many people here at a higher technical
level of discussion. But I am trying to couch it in terms of
your apparent understanding/confusion, and your examples.

"Richard Crowley" wrote in message
...

Sure you can. The "earth's crust" is a conductor just as a
piece of copper wire is. It is not quite as good as copper
wire, but megawatts of power are transmitted all over the
planet using the earth's crust as the return path of the circuit.

The power that runs the computer you are reading this on
is likely transmitted through the ground (on the return path
of the high-voltage side). When you see a single wire on
the power poles with taps going into the transformers, note
that the other side of the transformer is connected to a ground wire. The
electricity comes from the generator,
through the single wire along the poles, into the transformer
(the "destination"), and then returns through the earth's
crust back to the generator.

Are you sure about that? I've heard of some telephone systems that used the
earth as a conductor, but surely it would be hazardous to transmit
substantial amounts of AC power through the earth, and I've never heard of
it being done. People walking barefoot on the ground would be electrocuted.
There would be a constant risk of setting things on fire on the ground. And
the conductivity of the earth is very variable -- your power would fail when
the ground got dry.

As far as I know, all high-voltage power transmission systems are 3-phase
systems, with a fourth wire connected to the earth for safety purposes, but
no substantial current flowing through the earth.

On Sat, 11 Feb 2006 23:00:50 -0800, Richard Crowley burbled:

snip

Sure you can. The "earth's crust" is a conductor just as a piece of copper
wire is. It is not quite as good as copper wire, but megawatts of power
are transmitted all over the planet using the earth's crust as the return
path of the circuit.

The power that runs the computer you are reading this on is likely
transmitted through the ground (on the return path of the high-voltage
side). When you see a single wire on the power poles with taps going into
the transformers, note that the other side of the transformer is connected
to a ground wire. The electricity comes from the generator, through the
single wire along the poles, into the transformer (the "destination"), and
then returns through the earth's crust back to the generator.

snip

What confusion it causes when you use the same term for conflicting
purposes! Surely it is better to use the old (english) terms of "Earth"
and "Chassis" instead of the Americanism "Ground"? Far less confusing! ;-)

I'm not sure how your power system works (I think the US is basically
similar), but here in the UK we certainly don't use "Ground" in the way
that you describe for distribution. It would be highly dangerous as a high
current through the earth would produce a correspondingly high voltage
across any 2 points in its path e.g. your legs! You don't find any
(legal!) single wire power distribution at all in the uk.

HV 3-phase systems are usually run as just the 3 phases (it can be 6
wires, 2 each of the phases), from a delta winding on a transformer or
generator. At a substation there is a Delta/Star transformer. The centre
tap of the star windings is the Neutral connection and is earthed at the
sub (sometimes via a resistor or inductor). That neutral is then run for
local distribution with the 3 phases as a 4-wire "unbalanced" system.
Single phase loads are then connected phase-neutral and approximately
balanced over the 3 phases. Any 3-phase loads simply ignore the neutral
and run as "balanced" loads. In this way all neutral current is balanced
over the 3 phases, so it isn't necessary to run a neutral connection all
the way back to the generator or to depend on an earth connection to
carry any current. (This is a very basic description!)

HV switchgear is *always* bonded to a local earth mat or rods. This is to
make sure that in the event of an earth fault the local ground around the
switchgear is "pulled up" to a high voltage if necessary, so there is no
danger to life in touching the local metalwork. "Ground" isn't always at
zero volts, in fact, during a fault, it can be at several thousand volts
for a very short period of time!

There are cases of sheep and cows being killed simply because they were in
the same field as a pylon being struck by lightning. The resistivity of
the earth causes a voltage gradient around the pylon and an unlucky animal
can get its heart stopped because of the voltage between its front legs
acts as an uncontrolled defibrillator.

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info

"mick" wrote in message
news
On Sat, 11 Feb 2006 23:00:50 -0800, Richard Crowley burbled:

snip

Sure you can. The "earth's crust" is a conductor just as a piece of
copper
wire is. It is not quite as good as copper wire, but megawatts of
power
are transmitted all over the planet using the earth's crust as the
return
path of the circuit.

The power that runs the computer you are reading this on is likely
transmitted through the ground (on the return path of the
high-voltage
side). When you see a single wire on the power poles with taps going
into
the transformers, note that the other side of the transformer is
connected
to a ground wire. The electricity comes from the generator, through
the
single wire along the poles, into the transformer (the
"destination"), and
then returns through the earth's crust back to the generator.

snip

What confusion it causes when you use the same term for conflicting
purposes! Surely it is better to use the old (english) terms of
"Earth"
and "Chassis" instead of the Americanism "Ground"? Far less confusing!
;-)

I'm not sure how your power system works (I think the US is basically
similar), but here in the UK we certainly don't use "Ground" in the
way
that you describe for distribution. It would be highly dangerous as a
high
current through the earth would produce a correspondingly high voltage
across any 2 points in its path e.g. your legs! You don't find any
(legal!) single wire power distribution at all in the uk.

http://en.wikipedia.org/wiki/Single_wire_earth_return

"mc" wrote ...
"Richard Crowley" wrote ...
The power that runs the computer you are reading this on
is likely transmitted through the ground (on the return path
of the high-voltage side). When you see a single wire on
the power poles with taps going into the transformers, note
that the other side of the transformer is connected to a ground wire.
The electricity comes from the generator,
through the single wire along the poles, into the transformer
(the "destination"), and then returns through the earth's
crust back to the generator.

Are you sure about that?

Absolutely.

I've heard of some telephone systems that used the earth as a
conductor, but surely it would be hazardous to transmit substantial
amounts of AC power through the earth,

Why? By the most obvious definition, it is at "ground-potential"
and cannot cause harm (unless you take a long metal antenna
mast and touch the other side of the circuit 35 feet up in the air!)

and I've never heard of it being done.

Nevertheless, millions of watt-hours are flowing through
your planet's crust as you read these words. Perhaps even
under your feet.

People walking barefoot on the ground would be electrocuted.

You need a complete circuit to be electrocuted. If you are not
touching the other side of the circuit, no current can flow and
you are safe from electrocution.

There would be a constant risk of setting things on fire on the
ground.

How? (Hint: this is clearly not the case as we don't see
examples of spontaneous combustion from current flowing
through the earth.)

And the conductivity of the earth is very variable --
your power would fail when the ground got dry.

Think deeper.

As far as I know, all high-voltage power transmission systems are
3-phase systems, with a fourth wire connected to the earth for safety
purposes, but no substantial current flowing through the earth.

http://en.wikipedia.org/wiki/Single_wire_earth_return

http://science.howstuffworks.com/power9.htm shows a
ground-referenced power distribution system which also
includes a ground wire strung along the poles. In my part
of the country, they don't use the extra ground wire shown
in the photo, they rely on actual earth ground for the return
path.

On Sun, 12 Feb 2006 10:00:36 -0800, Richard Crowley burbled:

snip

http://en.wikipedia.org/wiki/Single_wire_earth_return

Thanks Richard. Looks like we are both right :-)

http://www.answers.com/topic/electricity-distribution
"In New Zealand, Australia,Saskatchewan,Canada and South Africa, single
wire earth return systems (SWER) are used to electrify remote rural areas."

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info

I'm not sure how your power system works (I think the US is basically
similar), but here in the UK we certainly don't use "Ground" in the way
that you describe for distribution. It would be highly dangerous as a
high
current through the earth would produce a correspondingly high voltage
across any 2 points in its path e.g. your legs! You don't find any
(legal!) single wire power distribution at all in the uk.

http://en.wikipedia.org/wiki/Single_wire_earth_return

How about that. I never had heard of it. It still strikes me as dubious,
but I have no doubt there are people who have made it work.

I would not like to be a sheep grazing under such a line. Of course, I
would not like to be a sheep anyhow.

People walking barefoot on the ground would be electrocuted.

You need a complete circuit to be electrocuted. If you are not
touching the other side of the circuit, no current can flow and
you are safe from electrocution.

I was thinking about voltage gradients, but doing the math, I see you're
right.

The resistance of the earth isn't zero. Suppose you have a 12,000-volt
earth-return line that is 12,000 feet long (about 2 nautical miles). Then
you have a voltage gradient of 1 volt per foot, which is not going to be
hazardous unless somehow (using fences, guy wires or something) you got
yourself connected to two points maybe 100 feet apart.

Also, I gather they limit the current to something much less than 1 amp.

mc wrote:

I'm not sure how your power system works (I think the US is basically
similar), but here in the UK we certainly don't use "Ground" in the way
that you describe for distribution. It would be highly dangerous as a
high
current through the earth would produce a correspondingly high voltage
across any 2 points in its path e.g. your legs! You don't find any
(legal!) single wire power distribution at all in the uk.

http://en.wikipedia.org/wiki/Single_wire_earth_return


How about that. I never had heard of it. It still strikes me as dubious,
but I have no doubt there are people who have made it work.

I suspect that Mr. Crowley is an American as the Wikipedia article
doesn't refer to the United Kingdom. I can see a single wire earth
return from my window. It keeps sheep in their field. That's about
the only such thing you'll find here.

--
Eiron

I have no spirit to play with you; your dearth of judgment renders you
tedious - Ben Jonson.

"mc" wrote...
The resistance of the earth isn't zero. Suppose you have a
12,000-volt earth-return line that is 12,000 feet long (about 2
nautical miles). Then you have a voltage gradient of 1 volt per foot,
which is not going to be hazardous unless somehow (using fences, guy
wires or something) you got yourself connected to two points maybe 100
feet apart.

If your had your 12KV all dissipated through the earth, you
would have nothing coming out at the other end and there
would be no point in even constructing the power line, now
would there? Hint: Ideally there is ZERO voltage potential
between the two ends of any conductor, whether it is a piece
of copper, or a segment of the earth's crust. Anything above
zero represents loss. Loss of current, voltage, power, and $$$

Also, I gather they limit the current to something much less than 1
amp.

Hardly. The average neighborhood pole transformer runs
8~10A on the primary (high voltage) side.

Mega-watts of power over very long distances at high-voltage
DC using earth return ground.

http://en.wikipedia.org/wiki/High_vo...earth_ret urn

Here is an article about the one that starts where I live...
http://en.wikipedia.org/wiki/Pacific_Intertie

"Richard Crowley" wrote in message
...
"mc" wrote...
The resistance of the earth isn't zero. Suppose you have a 12,000-volt
earth-return line that is 12,000 feet long (about 2 nautical miles).
Then you have a voltage gradient of 1 volt per foot, which is not going
to be hazardous unless somehow (using fences, guy wires or something) you
got yourself connected to two points maybe 100 feet apart.

If your had your 12KV all dissipated through the earth, you
would have nothing coming out at the other end and there
would be no point in even constructing the power line, now
would there? Hint: Ideally there is ZERO voltage potential
between the two ends of any conductor, whether it is a piece
of copper, or a segment of the earth's crust. Anything above
zero represents loss. Loss of current, voltage, power, and $$$

Good point; I was thinking of the maximum possible.

On Sun, 12 Feb 2006 14:54:47 -0500, "mc"
wrote:


"Richard Crowley" wrote in message
...
"mc" wrote...
The resistance of the earth isn't zero. Suppose you have a 12,000-volt
earth-return line that is 12,000 feet long (about 2 nautical miles).
Then you have a voltage gradient of 1 volt per foot, which is not going
to be hazardous unless somehow (using fences, guy wires or something) you
got yourself connected to two points maybe 100 feet apart.

If your had your 12KV all dissipated through the earth, you
would have nothing coming out at the other end and there
would be no point in even constructing the power line, now
would there? Hint: Ideally there is ZERO voltage potential
between the two ends of any conductor, whether it is a piece
of copper, or a segment of the earth's crust. Anything above
zero represents loss. Loss of current, voltage, power, and $$$

Good point; I was thinking of the maximum possible.


Dunno if it has been mentioned, but these high voltage transmission
lines are all three phase. When they are perfectly balanced, they
don't need an earth wire, as there is no earth current. the earth wire
only needs to handle any out-of-balance residue.

d

Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote ...

Dunno if it has been mentioned, but these high voltage transmission
lines are all three phase.

Actually, some are DC.

When they are perfectly balanced, they
don't need an earth wire, as there is no earth current. the earth wire
only needs to handle any out-of-balance residue.

Both balanced and unbalanced (earth-return) methods
are used in practice.

http://en.wikipedia.org/wiki/HVDC#Mo...d_earth_return
http://www.answers.com/topic/high-vo...direct-current

On Sun, 12 Feb 2006 11:10:28 -0800, Richard Crowley burbled:

snip

Mega-watts of power over very long distances at high-voltage DC using
earth return ground.

http://en.wikipedia.org/wiki/High_vo...earth_ret urn

Here is an article about the one that starts where I live...
http://en.wikipedia.org/wiki/Pacific_Intertie

Wow! Thanks - very interesting reading... We don't get to see anything
like that over here simply because the distances arn't long enough.

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info

"mick" wrote ...
Wow! Thanks - very interesting reading... We don't get to see anything
like that over here simply because the distances arn't long enough.

http://en.wikipedia.org/wiki/HVDC_Moyle
http://en.wikipedia.org/wiki/East_West_Interconnector

On Sun, 12 Feb 2006 19:59:37 +0000, Don Pearce burbled:

snip
Dunno if it has been mentioned, but these high voltage transmission lines
are all three phase. When they are perfectly balanced, they don't need an
earth wire, as there is no earth current. the earth wire only needs to
handle any out-of-balance residue.


On the UK system the Neutral carries out-of-balance current as far as the
sub - after that it is reflected onto the delta-connected phases. At this
point Neutral (the star point of the transformer secondary) is connected
to earth. So, strictly speaking, earth is not used as a conductor at all.

There are one or two earth wires run at the top of pylons. I don't know if
these actually connect to the pylon metalwork though.

At one time you used to be able to light a small torch bulb between
Neutral and a true earth (spike) in some areas, simply because of the volt
drop on the Neutral conductor (it was quite a distance between subs). Of
course, that didn't do through the meter! I don't think that's possible in
many places nowadays, but it may still be possible in some outlying areas.

The very large feeders mentioned by Richard are HV DC though, with one
variation using just earth return. Interesting system and, as he says,
carrying many MW.

--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info

In article , "mc" wrote:
When I think it needs to be:

audio_generating_source - conductor wire A - destination device -
conductor
wire B - audio_generating_source


That's what it is, and conductor wire B is the outer shield of the cable,
which is called "ground."

Is called ground or is it connected to ground?

I "think" (this thread has made be rethink a lot of stuff I thought I
understood) I understand what ground means in DC, or more specifically, in a
car's environment. "Ground" in that sense usually means (e.g., is synonomous
with) "the negative battery terminal" (unless you have a postivie-grounded
battery, which would indicate the positive battery terminal). For example, the
conection of say a car radio would generally be:

battery+ - conductor - radio - conductor - metal body of car (aka
"ground") - battery-
which completes the circuit.

I understand "ground" in DC circuits to be synonomous with either the
postive or negative battery terminal.

Audio systems do not have, or require, rods driven into the ground. Let go
of that concept. That is not what "ground" means with an audio signal. Let
go of that.

I have to figure out how to read old posts on usenet so I can re-read you
guys' advice over & over til I get it.

I guess I'm confused there. In all the books I've read, grounded
means it's connected to a metal rod stuck inside the earth's crust.

You don't really believe that. Else you would be asking why
your RCA and mini-jacks didnt have a wire running to a ground
rod.

Cause people say wire A or wire B is ground. The elements in an eletronics
thing would have a wire connected to the chassis of the container/box & the
container would be connected to the third wire in an AC socket, which is in
turn connected to ground (as in the earth).

That makes me think that the circuit is:

audio_generating_source - conductor wire A - destination
device - conductor wire B

You seem to have a good grasp of what it takes to make a complete
"circuit". Did you look up the other dictionary definitions of the
word "circuit"?

I felt that my above description did not meet the requirements of
circuit is why I am confused.

Sure you can. The "earth's crust" is a conductor just as a
piece of copper wire is. It is not quite as good as copper
wire, but megawatts of power are transmitted all over the
planet using the earth's crust as the return path of the circuit.

The power that runs the computer you are reading this on
is likely transmitted through the ground (on the return path
of the high-voltage side). When you see a single wire on
the power poles with taps going into the transformers, note
that the other side of the transformer is connected to a
ground wire. The electricity comes from the generator,
through the single wire along the poles, into the transformer
(the "destination"), and then returns through the earth's
crust back to the generator.

Generator.A - transformer - "earth" - Generator.B

I can see the electrons flowing out of terminal A and returning back to B. But
I can't see electrons flowing out of terminal B and returning to A, even if
the earth is a conductor. Hmm...maybe that's what I'm missing...if it's a
conductor, it conducts electricity (no matter what it is?) If I just take the
earth to mean wire, I think I got it?

OK...are you saying that when (a) is +12V, if (b) was not
connected to ground it should be -12V. But if it is connected
to ground, it may be -14V?

No. When the signal is at "+12V", ALL the circuit is at +12V.
A few milliseconds later it might be -12V, and then ALL the
circuit will be -12V.

I don't know what I was thinking when I wrote that....


* Conductors DO NOT generate signals.
Understand that.

OK, so which is it? Do you *really* understand that
conductors do not generate signals, or do you believe
that connecting something to ground is "adding 2 volts"?
I don't know how to reply to you when even you don't
know what you believe (or not)?

I don't know html
works in usenet, but
img src="http://img380.imageshack.us/img380/5387/rcaground9cz.gif"

is an mspaint "schematic" of what I think when I hear "ground" in an AC
circuit.

1. is that how an rca plug looks when connected in the real world?
2. if so, where is the groudn going (to the chassis?)


If you mean (2), then people ground things to...
a) to use a convienent return path for power and signals.
For example, the outside of your RCA jacks or mini-phone
plugs, etc. Or virtually everything in your car.
b) to provide a common reference point for various
pieces of equipment.
c) to "shield" things from interference, similar to (1)a)
above.

So in a stereo minijack plug, how does each channel come from one conductor
(called the common ground)? Say the audio signal is like this (with a smooth
sine wave in-betwen)
1. left = +5V, right=+10V
2. left = 0V, right = +5V
3. left = -5V, right = 0V
4. left= 0V, right = -5V
4. left= +5V, right = -10V
4. left= 0V, right = -5V
4. left= -5V, right = 0V

If a positive voltage means the specific signal flows from
left_conductor - common ground / right_conductor - common ground...

...how can a negative voltage mean a specific signal flows from common
ground - left/right conductor if each channel has differing values at each
points? Or is it more of a "pulling" in electrons than a "pushing" electrons?
e.g., when the flow is from common ground - channel, it's pulling in X or Y
volts, but when flow is from signal-common ground, it's pushing out X or Y
volts? If the push/pull analogy works, I think I understand.


This is a very simplistic and even *******ized explanation
and can be blasted by many people here at a higher technical
level of discussion. But I am trying to couch it in terms of
your apparent understanding/confusion, and your examples.

Thanks for bearing with me...it's very hard on me (and disappointing to
myself) that I don't understand this stuff since I want to be an EE major.

"infamis" wrote ...
Is called ground or is it connected to ground?

Those are two different things. You must differentiate
between them to really understand what is being stated.

Note that you can say the the engine block in your car
is "grounded" to the chassis. But the chassis is never
actually connected to "earth/ground" unless you crash
your car into a ditch, etc.

I understand "ground" in DC circuits to be synonomous
with either the postive or negative battery terminal.

A circuit doesn't require a "ground", nor must it be called
that.

Take the case of a flashlight ("torch" in the UK). The most
simple form of an electrical circuit. A battery of cell(s)
connected through a switch to a light-bulb, and then the
current returning to the battery through the case. There
is no "ground" here unless you wish to be pedantic. You
could refer to the case as a "common" if you wish, but it
is such a simple circuit, there is little point.

So assuming a metal case, turn on the flashlight/torch.
Now touch the case to faucet in your kitchen. You have
now connected the common/ground of the circuit to
actual ground/earth. Did it change anything? Did the
light get brighter? Dimmer? No, no, and no.

"Grounding" ("earthing" in the UK) one point in a circuit
to actual ground/earth does nothing to the flow of current
in the circuit, no matter whether AC or DC.

Try to resist confusing a simple common circuit connection
(such as the metal chassis of a piece of electronic equipment)
with the concept of connecting things to ground rods
pounded into the earth's crust.

"infamis" wrote in message
. com...
In article , "mc"
wrote:
When I think it needs to be:

audio_generating_source - conductor wire A - destination device -
conductor
wire B - audio_generating_source


That's what it is, and conductor wire B is the outer shield of the cable,
which is called "ground."

Is called ground or is it connected to ground?

The former. It is not connected to the earth.

I "think" (this thread has made be rethink a lot of stuff I thought I
understood) I understand what ground means in DC, or more specifically, in
a
car's environment. "Ground" in that sense usually means (e.g., is
synonomous
with) "the negative battery terminal" (unless you have a postivie-grounded
battery, which would indicate the positive battery terminal). For example,
the
conection of say a car radio would generally be:

Ground means ANY point in the circuit which WE CHOOSE to ALWAYS connect one
side of our voltmeter to. Ground has no physical reality. Ground is merely
the arbitrary choice of a point in the circuit. In audio, the outer shields
of all the cables are connected together, so we choose that point in the
circuit to designate as ground.


battery+ - conductor - radio - conductor - metal body of car (aka
"ground") - battery-
which completes the circuit.

I understand "ground" in DC circuits to be synonomous with either the
postive or negative battery terminal.

In a car, yes. But "ground" means "arbitrarily chosen reference point" and
I can imagine circuits in which the most logical choice of "ground" is not
connected to either side of the battery. Admittedly, they are fairly
unusual circuits, such as double-ended power supplies built from a single
battery.

Audio systems do not have, or require, rods driven into the ground. Let
go
of that concept. That is not what "ground" means with an audio signal.
Let
go of that.

I have to figure out how to read old posts on usenet so I can re-read you
guys' advice over & over til I get it.

Skip the long digression about electrical power transmission lines, unless
you like long digressions.

I think the problem is simply that you are attributing too much meaning to
the word "ground."

One thing to cling to is this: Audio cables are each 2 conductors. The
inner wire is one conductor and the outer shield is the other one. Two
ordinary wires would work, but they would pick up more hum. To minimize hum
pickup, we make one conductor hollow and put the other one inside it.

The second thing to cling to is this: AC doesn't require any more wires than
DC. Imagine connecting a DC battery (such as an AA cell) to 2 wires which
will deliver power to its circuit (a light bulb). Now swap the battery back
and forth in its holder (put it in forward, then backward). Either way, it
only needs 2 wires. Imagine somebody who could swap the battery back and
forth hundreds of times per second. That would be AC. Still only 2 wires.

Notice that this light bulb circuit has no "ground" until YOU CHOOSE some
point in it to designate as "ground." That is your choice and is simply a
name you give to one point in the circuit. The laws of physics do not make
reference to "ground."

Now remember again what I said about the 4-terminal amplifier. Imagine a
little amplifier to which you connect a microphone (which has 2 wires coming
out of it) and a speaker (which also has 2 wires). The mic goes to
terminals A and B and the speaker goes to terminals C and D. On opening up
the amplifier, you find that B and D are tied together inside. That is, B
and D are a single point in the circuit which is "common" (shared) between
both input and output.

Well... because that point in the circuit (B and D) is common to input and
output, it is convenient to connect the cable shields to it (so that the
inner conductors of the cables go to A and C); then all the cable shields
are connected together, which is a Good Thing for minimizing hum pickup.

And we call that point in the circuit "ground."

In audio, "ground" means "common to input and output signals," which is what
B (alias D) is in this circuit.

That's all there is to it. Rods in the earth have essentially nothing to do
with audio.

Enjoy!

I don't know html
works in usenet, but
img src="http://img380.imageshack.us/img380/5387/rcaground9cz.gif"
is an mspaint "schematic" of what I think when I hear "ground" in an AC
circuit.

1. is that how an rca plug looks when connected in the real world?

Yes, exactly.

2. if so, where is the groudn going (to the chassis?)

It need not go anywhere else. The ground symbol simply means "this is the
point we have chosen to measure voltages against."

In practice, as in my other message, it's the common side of numerous inputs
and outputs of the amplifier. See:

www.ai.uga.edu/mc/temp/ground.jpg

and also

www.ai.uga.edu/mc/temp/ground.pdf

for more elucidation. For hum shielding, it will *usually* be connected to
the chassis, but it *need not* be connected to power line ground, and in
fact, to eliminate ground loops, audio equipment usually does not use power
line ground. (Ground loops are discrepancies between "ground" in one place
and another, like 2 outlets in the same room.)

..how can a negative voltage mean a specific signal flows from common
ground - left/right conductor if each channel has differing values at
each
points? Or is it more of a "pulling" in electrons than a "pushing"
electrons?

Exactly! You can pull electrons as well as push them. Electricity does not
consist of electrons. It consists of the *movement* of electrons or other
charged particles. In a wire, the charged particles are electrons. In a
battery, they are ions. Machines can be built where the charge is carried
by protons, or whatever.

"infamis" wrote...
Cause people say wire A or wire B is ground....

Rememer that there are several *different* ways of using
the word "ground". Don't assume that they all mean the
same thing. Many words in English (and likely other
languages also) have several different meanings. We
must determine which meaning is appropriate or we
will be confused.

I felt that my above description did not meet the requirements of
circuit is why I am confused.

Any connection that conveys a signal/power from one
point to another is a "circuit".

Generator.A - transformer - "earth" - Generator.B

One terminal of the generator is connected to a ground rod.
The other terminal is connected to a wire that travels many
miles across countless power poles to the transformer which
supplies your home. That wire connects to the primary of the
transformer. The other side of the primary conects to ground
at the base of the pole.

The current starts at the generator, travels many miles over
the power pole wires, connects to the transformer outside
your house, then then current travels back many miles through
the crust of the earth to the generator completing the "circuit".
A "circuit" is a circular path. I urge you AGAIN to read all the
dictionary definitions of the word "circuit".

img src="http://img380.imageshack.us/img380/5387/rcaground9cz.gif"

is an mspaint "schematic" of what I think when I hear "ground" in an
AC
circuit.

1. is that how an rca plug looks when connected in the real world?

For the purposes of your discussion, yes.

2. if so, where is the groudn going (to the chassis?)

Your ground symbol is shown connected to one "node"
of your circuit. The circuit would work just as well if
it were not there.

Don't really know what you mean by "where is it going"?
Your circuit would be complete and operational without
your "ground" connection. Where is *what* going?


..how can a negative voltage mean a specific signal flows from
common
ground - left/right conductor if each channel has differing values at
each
points? Or is it more of a "pulling" in electrons than a "pushing"
electrons?
e.g., when the flow is from common ground - channel, it's pulling in
X or Y
volts, but when flow is from signal-common ground, it's pushing out X
or Y
volts? If the push/pull analogy works, I think I understand.

Take the circuit you drew. Now make a mirror image
of it and connect the two "grounds" together. That is
what you have with a stereo mini-jack. Each circuit
(the left circuit and the right circuit) is a complete
path in itself and doesn't care what the other one is
doing or whether it is connected to it or not. Follow
the current flow around the "circuit".

Just as you can take your original diagram and either
connect the ground point to the earth, or not. The
circuit doesn't care because the current is flowing
through the circular path (the "circuit") and is complete
in itself.

The common node of the stereo mini-phone connector
(the "sleeve") carries the return current for BOTH the
left channel "circuit" and the right channel "circuit".

On Sun, 12 Feb 2006 13:22:38 -0800, Richard Crowley burbled:

"mick" wrote ...
Wow! Thanks - very interesting reading... We don't get to see anything
like that over here simply because the distances arn't long enough.

http://en.wikipedia.org/wiki/HVDC_Moyle
http://en.wikipedia.org/wiki/East_West_Interconnector

grin That's close enough... Looks like the runs round here are
integrated return though. Not that long a distance.

That is some *serious* HV engineering in the Siemens literature! Anyone
fancy a 275mH 3000A choke to smooth their psu?

/me is happy with lots of copper and iron. Can't get the hang of computers
and direct light-triggered thyristors... ;-)
--
Mick
(no M$ software on here... :-) )
Web: http://www.nascom.info

In article , "mc" wrote:
It need not go anywhere else. The ground symbol simply means "this is the
point we have chosen to measure voltages against."

In practice, as in my other message, it's the common side of numerous inputs
and outputs of the amplifier. See:

www.ai.uga.edu/mc/temp/ground.jpg

and also

www.ai.uga.edu/mc/temp/ground.pdf

That jpeg helped a lot...I never knew the ground symbol was there as a
convenience to schematics-writers. I think my main point of misunderstanding
is that I'm trying to combine all meanings of "ground" into one. For the
original question, it's safe to say ground (physically) means nothing. The tip
or the shield can be "ground" (as long as all the other components follow that
schema, otherwise it wouldn't be "ground" since they would all be different).

Exactly! You can pull electrons as well as push them. Electricity does not
consist of electrons. It consists of the *movement* of electrons or other
charged particles. In a wire, the charged particles are electrons. In a
battery, they are ions. Machines can be built where the charge is carried
by protons, or whatever.

Right. I think I was also messing myself up by the way I visualized the
movement of the signal. I would think of it as a single electron moving around
in a circle, when it should be a "string" (like a shoe string with ends
tied to form a circle) rotating like a merry-go-round. Is that a correct way
of thinking about it?

In article , "Richard Crowley" wrote:
Rememer that there are several *different* ways of using
the word "ground". Don't assume that they all mean the
same thing. Many words in English (and likely other
languages also) have several different meanings. We
must determine which meaning is appropriate or we
will be confused.

Exactly. That's what I keep forgetting. But how would you know which meaning
of ground someone means if all you saw was the ground symbol on a schematic?
How would you know it meant ground as in the "reference" point (like the
shield of the RCA interconnect) or as a connection to the chassis/power line?
I guess it depends on the context, just like the definition of a particular
word depends on the context in which it's used? I guess I just don't know
enough to decipher which meaning (for now).


I felt that my above description did not meet the requirements of
circuit is why I am confused.

Any connection that conveys a signal/power from one
point to another is a "circuit".

Right, and since my original drawing didn't meet the definition of a circuit
was why I was confused (since I thought my drawing was the technically correct
of how stuff works). But now I understand I need not worry about that now
since I don't care about the earth (in this particular discussion).

Generator.A - transformer - "earth" - Generator.B

One terminal of the generator is connected to a ground rod.
The other terminal is connected to a wire that travels many
miles across countless power poles to the transformer which
supplies your home. That wire connects to the primary of the
transformer. The other side of the primary conects to ground
at the base of the pole.

The current starts at the generator, travels many miles over
the power pole wires, connects to the transformer outside
your house, then then current travels back many miles through
the crust of the earth to the generator completing the "circuit".
A "circuit" is a circular path. I urge you AGAIN to read all the
dictionary definitions of the word "circuit".

I get it. I think I was just disregarding the earth as a conductor since when
I think of conductor, I think shiny metal. I know it's wrong, as a conductor
is a material that has little resistivity to the flow of electrons.

Don't really know what you mean by "where is it going"?
Your circuit would be complete and operational without
your "ground" connection. Where is *what* going?

I was adding the "ground" definition as a connection to something called
ground (like for instance, the chassis). So my drawing would still be correct
if instead of the wire connecting the bottom terminal of the AC signal to the
bottom terminal of the amp, both the AC terminal & amp terminal had a short
line drawn connected to a "ground" symbol?

Take the circuit you drew. Now make a mirror image
of it and connect the two "grounds" together. That is
what you have with a stereo mini-jack. Each circuit
(the left circuit and the right circuit) is a complete
path in itself and doesn't care what the other one is
doing or whether it is connected to it or not. Follow
the current flow around the "circuit".

Just as you can take your original diagram and either
connect the ground point to the earth, or not. The
circuit doesn't care because the current is flowing
through the circular path (the "circuit") and is complete
in itself.

The common node of the stereo mini-phone connector
(the "sleeve") carries the return current for BOTH the
left channel "circuit" and the right channel "circuit".

Wow, I think I'm starting to get it.

"infamis" wrote in message
. com...

That jpeg helped a lot...I never knew the ground symbol was there as a
convenience to schematics-writers. I think my main point of
misunderstanding
is that I'm trying to combine all meanings of "ground" into one.

Exactly.

You can pull electrons as well as push them. Electricity does not
consist of electrons. It consists of the *movement* of electrons or other
charged particles. In a wire, the charged particles are electrons. In a
battery, they are ions. Machines can be built where the charge is carried
by protons, or whatever.

Right. I think I was also messing myself up by the way I visualized the
movement of the signal. I would think of it as a single electron moving
around
in a circle, when it should be a "string" (like a shoe string with ends
tied to form a circle) rotating like a merry-go-round. Is that a correct
way
of thinking about it?

Right. Or think of it as a bicycle chain. With DC, the big wheel always
turns the same direction, moving the electrons around the circuit. With AC,
the big wheel switches direction of rotation regularly.

"infamis" wrote in message
om...
In article , "Richard Crowley"
wrote:
Rememer that there are several *different* ways of using
the word "ground". Don't assume that they all mean the
same thing. Many words in English (and likely other
languages also) have several different meanings. We
must determine which meaning is appropriate or we
will be confused.

Exactly. That's what I keep forgetting. But how would you know which
meaning
of ground someone means if all you saw was the ground symbol on a
schematic?
How would you know it meant ground as in the "reference" point (like the
shield of the RCA interconnect) or as a connection to the chassis/power
line?

It means reference point unless it's very explicitly indicated that it means
something else. There is a different symbol (a sort of bent rectangular
pitchfork upside down) for connection to chassis. Connection to the earth
is so rare that you will not see it in ordinary circuit diagrams.