"Floyd L. Davidson" wrote in message
...
"operator jay" wrote:
"Floyd L. Davidson" wrote in message
...

The problem is that "direction" only has meaning when measured
in comparison some specific point of reference. If you have
three different reference points, one at the DC level, one at
the peak positive swing and one at the peak negative swing, you
have three very different views of "direction" for current flow:

Reference Direction
Point of flow
========= =====================================

Peak Pos All Negative

DC level Equal cycles of Positive and Negative

Peak Neg All Positive



I think "zero" is a good reference for current flow, and that the actual

Sure... now, can you define "zero"?


Put an ammeter there and it says zero. That's zero. Electrons bouncing
around in the conductor have an average net displacement, over time, of 0.

(absolute) direction can be measured. Voltages have the reference
issues.

E =IR

Since our resistance is fixed, it's the exact same issue, though
perhaps easier to understand, with voltage. (I gave some
consideration as to whether to post that with voltage or current
references, and since "AC" and "DC" use the term "current",
decided to go with current to avoid the easier path to the same
statement you are making.)


Current is a different issue from voltage because voltage is a relative
quantity. It is a type of measurement of a change in field between two
locations. Current is a rate of flow of charge at a single location (well,
typically, through a single Gaussian surface), and is measurable at that
location, and does not have the ambiguity that voltage has. It does not
need a reference. If I say that my toaster is running at 120V and 8A, you
may ask "120V relative to what" and I'll answer "neutral". You would not
ask "8A relative to what".

j

On Sun, 12 Jun 2005 12:21:01 -0500, "operator jay"
wrote:


Put an ammeter there and it says zero. That's zero. Electrons bouncing
around in the conductor have an average net displacement, over time, of 0.

"Put and ammeter there" and if it says +300mA to +800mA back and
forth, then it's Alternating Current, innit?

"Kitchen Man" wrote in message
news
On Sun, 12 Jun 2005 12:21:01 -0500, "operator jay"
wrote:


Put an ammeter there and it says zero. That's zero. Electrons bouncing
around in the conductor have an average net displacement, over time, of
0.

"Put and ammeter there" and if it says +300mA to +800mA back and
forth, then it's Alternating Current, innit?


It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that debate.
To me the terms involved are open to too many interpretations. As evidenced
in this thread, I suppose.

j

"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that debate.
To me the terms involved are open to too many interpretations. As evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC. You keep
talking about AP, and it isn't the same.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"Floyd L. Davidson" wrote in message
...
"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that
debate.
To me the terms involved are open to too many interpretations. As
evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC. You keep
talking about AP, and it isn't the same.

You are the one with the requirements, assertions, and definitions, not me.
Where are you coming up with them? If it's from the same place where
- zero current is not definable
- magnitude of current needs an outside reference
- voltage and current are for all practical purposes different expressions
of the same thing
- alter is the same thing as alternate
then I don't even want to know.

You need to come to realize there is no clear cut correct answer on this
'AC' vs 'DC' issue at this time. If there was one, there would be much more
consensus between people on what the correct answer is. This big long
thread would not have occurred. Now let's turn it around and look at it the
other way. This big long thread did occur. We can plainly see that there
is disagreement between groups on what exactly the precise meanings of AC
and DC entail. Therefore there effectively is no single exact definition
for "AC" or for "DC" that will allow us to resolve which is correct and
which is not correct.

Picture my flashlight, battery powered. Generally this is considered a dc
circuit. When I turn it on or off, there is 'change'. So is it in fact an
AC flashlight? If the battery starts to die there is a change so is it in
fact an AC battery? Etcetera. (These questions are rhetorical by the way).
I know better than to try to pin a strict name on these things where there
is not an (adequately) universal and strict definition.

On another note, how long are the days getting to be way up there? Do you
get continuous sunshine?

j

On Sun, 12 Jun 2005 22:59:18 -0500, "operator jay"
wrote:

You are the one with the requirements, assertions, and definitions, not me.

Actually, the ones with the requirements, assertions, and definitions
are codes and organizations such as the NEC and the IEEE, and the
bothersome universities that teach the stuff.

On this point:

Picture my flashlight, battery powered. Generally this is considered a dc
circuit. When I turn it on or off, there is 'change'. So is it in fact an
AC flashlight? If the battery starts to die there is a change so is it in
fact an AC battery? Etcetera. (These questions are rhetorical by the way).
I know better than to try to pin a strict name on these things where there
is not an (adequately) universal and strict definition.

You are talking about transients, and if you intend for the questions
to be rhetorical, then I think you should demonstrate some expertise
in the subject matter that shows why the questions' answers must be
obvious. I don't think they are, so I will answer the questions:

The behavior of the flashlight in your example is neither AC nor DC,
it is transient. The first case is the instantaneous step function
caused by the closing of a source to a circuit. The second case is a
long-term curved ramp caused by the decay of a voltage source. AC and
DC analyses are steady-state. AC analysis will never apply to the
example. DC analysis must be performed prior to the transient
analysis in order to provide a steady state model for the application
of time-sensitive mathematics.

There is quite a bit of information available on the web about circuit
analysis. Your curiosity is to be commended; you might consider a web
crawling adventure, or even an education in the field.

And hey operator jay, what do you operate? Not electrical
substations, I wouldn't guess.

--
Al Brennan

"If you only knew the magnificence of the 3, 6 and 9,
then you would have a key to the universe." Nicola Tesla

"Kitchen Man" wrote in message
...
On Sun, 12 Jun 2005 22:59:18 -0500, "operator jay"
wrote:

You are the one with the requirements, assertions, and definitions, not
me.

Actually, the ones with the requirements, assertions, and definitions
are codes and organizations such as the NEC and the IEEE, and the
bothersome universities that teach the stuff.

If you have definitions of AC and DC handy from IEEE or someone, stick them
on here. I'd say that the (apparent) widespread disagreement means that,
functionally, there is no single pervasive definition for these terms, but
it would be interesting to see if some of these bodies have published
definitions. It would be really interesting if they had definitions, and
they didn't quite agree with one another, or if they were "wishy-washy".


On this point:

Picture my flashlight, battery powered. Generally this is considered a
dc
circuit. When I turn it on or off, there is 'change'. So is it in fact
an
AC flashlight? If the battery starts to die there is a change so is it
in
fact an AC battery? Etcetera. (These questions are rhetorical by the
way).
I know better than to try to pin a strict name on these things where
there
is not an (adequately) universal and strict definition.

You are talking about transients, and if you intend for the questions
to be rhetorical, then I think you should demonstrate some expertise
in the subject matter that shows why the questions' answers must be
obvious. I don't think they are, so I will answer the questions:

"show why the answers must be obvious" sounds like a peculiar concept. An
obvious answer inherently needs no explaining.


The behavior of the flashlight in your example is neither AC nor DC,
it is transient. The first case is the instantaneous step function
caused by the closing of a source to a circuit. The second case is a
long-term curved ramp caused by the decay of a voltage source. AC and
DC analyses are steady-state. AC analysis will never apply to the
example. DC analysis must be performed prior to the transient
analysis in order to provide a steady state model for the application
of time-sensitive mathematics.

You feel that neither AC nor DC is correct as a description for the
flashlight behavior. I wonder whether there is a sufficiently definitive
(and also agreeable) meaning of "AC" or of "DC" that would merit this
position. I infer from other posts that there are people who would say it
is DC. There may be others who would say it is AC. So a statement of fact
that it is neither AC nor DC is suspect. By the way, my rhetorical
questions were actually whether it is an AC flashlight and whether it is an
AC battery. The point of this was (I thought obviously) to illuminate the
difficulty in declaring some things to be AC or to be DC. There is a
certain ridiculousness (I thought obviously) in calling a flashlight AC or
in calling a battery AC. Yet it would be awkward (I thought obviously) in
adhering to calling it DC if one's description of DC was that the (voltage /
current) would essentially remain constant. Thus my (possibly obvious)
point and my rhetoricals. I'll work on them. Your response did not seem to
conradict my point.


There is quite a bit of information available on the web about circuit
analysis. Your curiosity is to be commended; you might consider a web
crawling adventure, or even an education in the field.

The web has lots of information and lots of misinformation, I think you'd
agree. I'm not sure that I have displayed curiosity in these posts. An
education in the field of circuit analysis? No, thanks, you go ahead.


And hey operator jay, what do you operate? Not electrical
substations, I wouldn't guess.


That's remarkably funny. What do you operate? Not your brain I wouldn't
guess.

j

"operator jay" wrote:
"Floyd L. Davidson" wrote:

Picture my flashlight, battery powered. Generally this is considered a dc
circuit. When I turn it on or off, there is 'change'.

You were doing pretty good up to that point.

So is it in fact an
AC flashlight?

No. But that doesn't mean there is never any AC present in the
circuit.

It happens that with a battery powered flashlight that is rare
(but predictable too), and of no consequence whatever. It can
be ignored in design and operation of the flashlight. But that
doesn't mean there is never any AC in the circuit, or that there
are no circuits where it is significant.

If the battery starts to die there is a change so is it in
fact an AC battery? Etcetera. (These questions are rhetorical by the way).
I know better than to try to pin a strict name on these things where there
is not an (adequately) universal and strict definition.

Every time you flip the switch on or off, there is AC in that
circuit.

You can probably prove it too, relatively easy. Tune an AM
receiver to a frequency where no station is being received, and
hold the flashlight up close to the antenna. Flip it on and off
a few times. I suspect, though I haven't actually tried this,
that you'll hear a pop in the radio's speaker almost every time
you flip the switch. That is because some of the AC produced by
flipping that switch is RF.

On another note, how long are the days getting to be way up there? Do you
get continuous sunshine?

It's been 24 hours of daylight for quite some time now. The sun
hasn't actually gone down for a month (May 10th), but of course
we had 24 hours of light long before that. The next time it
gets below the horizon will be August 1, and it will be late
August before it gets "dark".

The temperature is 30F right now, with a reported 18 mph wind and
fog. It was gusting up to 30 mph last night. It probably won't get
much warmer than maybe 36F today.

That is actually very comfortable weather, mostly because it is
unlikely to rain. I hate getting wet... :-)


--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"Floyd L. Davidson" wrote in message
...
"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that
debate.
To me the terms involved are open to too many interpretations. As
evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC. You keep
talking about AP, and it isn't the same.


'Alternating' is not the same as 'altering'. "Alternating current" is an
electrical current where the magnitude and *direction* [emphasis added]
varies cyclically.

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

One may 'alter' the magnitude of a DC current without it becoming
'alternating current'

daestrom

On Mon, 13 Jun 2005 11:49:58 GMT, "daestrom"
wrote:


"Floyd L. Davidson" wrote in message
...
"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that
debate.
To me the terms involved are open to too many interpretations. As
evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC. You keep
talking about AP, and it isn't the same.


'Alternating' is not the same as 'altering'. "Alternating current" is an
electrical current where the magnitude and *direction* [emphasis added]
varies cyclically.

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

One may 'alter' the magnitude of a DC current without it becoming
'alternating current'

The problem with that definition is that it is unnecessarily limiting.
You can find other sources where the definition reads "magnitude *or*
direction," the latter which I believe to be more correct. If the
signal is steady state, then the current that changes magnitude but
never direction is simply an AC signal with a DC component greater in
positive amplitude than the negative peak of the AC component.

--
Al Brennan

"If you only knew the magnificence of the 3, 6 and 9,
then you would have a key to the universe." Nicola Tesla

"Kitchen Man" wrote in message
...
On Mon, 13 Jun 2005 11:49:58 GMT, "daestrom"
wrote:


"Floyd L. Davidson" wrote in message
...
"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that
debate.
To me the terms involved are open to too many interpretations. As
evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC. You keep
talking about AP, and it isn't the same.


'Alternating' is not the same as 'altering'. "Alternating current" is an
electrical current where the magnitude and *direction* [emphasis added]
varies cyclically.

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

One may 'alter' the magnitude of a DC current without it becoming
'alternating current'

The problem with that definition is that it is unnecessarily limiting.
You can find other sources where the definition reads "magnitude *or*
direction," the latter which I believe to be more correct. If the
signal is steady state, then the current that changes magnitude but
never direction is simply an AC signal with a DC component greater in
positive amplitude than the negative peak of the AC component.

--
Al Brennan

"If you only knew the magnificence of the 3, 6 and 9,
then you would have a key to the universe." Nicola Tesla

In any case, what you have to do in analysis is to treat each frequency
separately, including the 0 frequency term.
What's the big deal.??

--
Don Kelly

remove the urine to answer

On Sun, 12 Jun 2005 18:28:16 -0800, (Floyd L.
Davidson) wrote:

"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that debate.
To me the terms involved are open to too many interpretations. As evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC.

---
No, if the direction of charge flow alternates between two states,
then it's Alternating Current.
---

You keep talking about AP, and it isn't the same.

---
Yes, it is. In order for the current in a load to alternate, the
polarity of the generator's output voltage must alternate as well.

--
John Fields
Professional Circuit Designer

John Fields wrote:
On Sun, 12 Jun 2005 18:28:16 -0800, (Floyd L.
Davidson) wrote:

"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that debate.
To me the terms involved are open to too many interpretations. As evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC.

---
No, if the direction of charge flow alternates between two states,
then it's Alternating Current.

That fits my definition, but not yours! Are you changing your definition
or is that just a momentary bit of logical thought?

The states do *not* have to be plus and minus polarity. Just different
current levels...

---

You keep talking about AP, and it isn't the same.

---
Yes, it is. In order for the current in a load to alternate, the
polarity of the generator's output voltage must alternate as well.

Sure. But it doesn't need to change polarity. All it needs to do
is change level.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

On Mon, 13 Jun 2005 07:47:51 -0800, (Floyd L.
Davidson) wrote:

John Fields wrote:
On Sun, 12 Jun 2005 18:28:16 -0800, (Floyd L.
Davidson) wrote:

"operator jay" wrote:

It is not changing polarity. I would hesitate to call it alternating
current. On the "dc sine wave" issue, I wouldn't even get into that debate.
To me the terms involved are open to too many interpretations. As evidenced
in this thread, I suppose.

Where *do* you get this requirement for changing polarity? We
don't call it "Alternating Polarity", we call it "Alternating
Current". If the current is being altered, it's AC.

---
No, if the direction of charge flow alternates between two states,
then it's Alternating Current.

That fits my definition, but not yours! Are you changing your definition
or is that just a momentary bit of logical thought?

---
Try not to be a stupid ****. Flames will get you nothing back but more
flames. Is that what you want?
---

The states do *not* have to be plus and minus polarity. Just different
current levels...

---
Go back and read it again. Concentrate especially hard on the part
about the _direction_ of charge flow alternating between two states
and maybe you'll get it.
---

You keep talking about AP, and it isn't the same.

---
Yes, it is. In order for the current in a load to alternate, the
polarity of the generator's output voltage must alternate as well.

Sure. But it doesn't need to change polarity. All it needs to do
is change level.

---
I'm starting to think you're having a real problem with reading
comprehension. I write that for the current in a load to alternate,
the polarity of the generator's output voltage must alternate as well,
and then you agree but state that it doesn't need to change polarity.

Don't you understand that an alternation in polarity means that the
polarity changed???

--
John Fields
Professional Circuit Designer

"John Fields" wrote in message
...
....
Yes, it is. In order for the current in a load to alternate, the
polarity of the generator's output voltage must alternate as well.


Consider a voltage source with output Eo = 2 + sin(w t)
driving a capacitor as its load. The voltage does not
alternate but the current will.

--
--Larry Brasfield
email:
Above views may belong only to me.

On Mon, 13 Jun 2005 11:20:43 -0700, "Larry Brasfield"
wrote:

"John Fields" wrote in message
...
...
Yes, it is. In order for the current in a load to alternate, the
polarity of the generator's output voltage must alternate as well.


Consider a voltage source with output Eo = 2 + sin(w t)
driving a capacitor as its load. The voltage does not
alternate but the current will.

---
True, but in the context of the post from which the excerpt came
capacitive loads had not yet been introduced into the discussion.

--
John Fields
Professional Circuit Designer

"operator jay" wrote:
"Floyd L. Davidson" wrote in message
...
"operator jay" wrote:
"Floyd L. Davidson" wrote in message
...

The problem is that "direction" only has meaning when measured
in comparison some specific point of reference. If you have
three different reference points, one at the DC level, one at
the peak positive swing and one at the peak negative swing, you
have three very different views of "direction" for current flow:

Reference Direction
Point of flow
========= =====================================

Peak Pos All Negative

DC level Equal cycles of Positive and Negative

Peak Neg All Positive



I think "zero" is a good reference for current flow, and that the actual

Sure... now, can you define "zero"?


Put an ammeter there and it says zero. That's zero. Electrons bouncing
around in the conductor have an average net displacement, over time, of 0.

Is this an AC ammeter, or a DC ammeter? (And isn't that just a voltmeter
anyway, in most actual cases????) Hmmm...

(absolute) direction can be measured. Voltages have the reference
issues.

E =IR

You can't escape the fact that voltage and current are joined at
the hip, they are for all practical purposes different expressions
of the same thing. Whatever affects one *has* to have affected the
other.

Since our resistance is fixed, it's the exact same issue, though
perhaps easier to understand, with voltage. (I gave some
consideration as to whether to post that with voltage or current
references, and since "AC" and "DC" use the term "current",
decided to go with current to avoid the easier path to the same
statement you are making.)


Current is a different issue from voltage because voltage is a relative
quantity.

No more or less than current. They are joined at a hip called
Ohm's Law.

It is a type of measurement of a change in field between two
locations. Current is a rate of flow of charge at a single location (well,
typically, through a single Gaussian surface), and is measurable at that
location, and does not have the ambiguity that voltage has. It does not
need a reference. If I say that my toaster is running at 120V and 8A, you
may ask "120V relative to what" and I'll answer "neutral". You would not
ask "8A relative to what".

8 Amps from where? To where? Through were?

Relative to where?

Since we can discuss current using only voltage as the variable
(resistance being a constant in this example), *anything* you
can say about voltage is directly related to current.

One of the overall things that you *have* to keep in mind is
that periodic reality checks are necessary. One of them is the
fact, repeated by many in this thread, that "DC sine wave" is a
contradiction of terms. If your definition makes it possible,
your definition *can't* be right.

My point still stands, that if the current is changing, it is by
definition AC, and current not changing is DC. Trying to look
at it as DC is all in one direction and anything else is AC,
doesn't work.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

On Sun, 12 Jun 2005 14:00:23 -0800, (Floyd L.
Davidson) wrote:


My point still stands, that if the current is changing, it is by
definition AC, and current not changing is DC. Trying to look
at it as DC is all in one direction and anything else is AC,
doesn't work.

---
Your point is flawed. Alternating Current, by definition, causes
electrons to move in one direction for a time, and then to reverse
direction for a time.

The sinusoidally varying unipolar voltage under consideration _always_
forces electrons to move in one direction only.

Since the voltage varies, the current will also, but the _direction_
in which the electrons are travelling will never change.

That means that the signal is DC. A varying DC, but DC nonetheless.

--
John Fields
Professional Circuit Designer

John Fields wrote:
On Sun, 12 Jun 2005 14:00:23 -0800, (Floyd L.
Davidson) wrote:

My point still stands, that if the current is changing, it is by
definition AC, and current not changing is DC. Trying to look
at it as DC is all in one direction and anything else is AC,
doesn't work.

---
Your point is flawed. Alternating Current, by definition, causes
electrons to move in one direction for a time, and then to reverse
direction for a time.

That isn't true.

The sinusoidally varying unipolar voltage under consideration _always_
forces electrons to move in one direction only.

A non-sequitor.

Since the voltage varies, the current will also, but the _direction_
in which the electrons are travelling will never change.

If it varies, it's AC.

That means that the signal is DC. A varying DC, but DC nonetheless.

If there is such a think as "varying DC", connect a load to
it... through a capacitor. Now, how do you describe the effect
that load has on your "varying DC". The load see's *only* AC,
even according to your definition. That AC came from somewhere,
and it certainly was not generated by the capacitor.

That's because AC is *not* defined by any change in direction,
but only by a rate of movement change.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"Floyd L. Davidson" wrote in message
...
John Fields wrote:
On Sun, 12 Jun 2005 14:00:23 -0800, (Floyd L.
Davidson) wrote:

My point still stands, that if the current is changing, it is by
definition AC, and current not changing is DC. Trying to look
at it as DC is all in one direction and anything else is AC,
doesn't work.

---
Your point is flawed. Alternating Current, by definition, causes
electrons to move in one direction for a time, and then to reverse
direction for a time.

That isn't true.

It is true by most definitions of 'Alternating Current'.
http://en.wikipedia.org/wiki/Alternating_current

'Alternating' means both magnitude and direction vary over time. A current
that varies in magnitude but not direction is not 'alternating'.

Since the voltage varies, the current will also, but the _direction_
in which the electrons are travelling will never change.

If it varies, it's AC.

Only by your apparent definition. But your definition does not agree with
the established industry.


That means that the signal is DC. A varying DC, but DC nonetheless.

If there is such a think as "varying DC", connect a load to
it... through a capacitor. Now, how do you describe the effect
that load has on your "varying DC". The load see's *only* AC,
even according to your definition. That AC came from somewhere,
and it certainly was not generated by the capacitor.

By adding a capacitor in series, you have altered the circuit. The
capacitor filters out the DC component of a the original varying DC voltage
applied. The capacitor has a varying DC voltage across it, but it never
changes polarity (you can use an electrolytic capacitor that is polarity
sensitive without damage).

The current through the resulting series circuit *does* alternate in
magnitude and *direction*, even though the voltage applied to the circuit
varies in magnitude only. So yes, the 'AC came from somewhere'. But that
doesn't mean the applied voltage is AC. Such logic is flawed. There is no
'law of conservation of AC' that says it can't be 'generated by the
capacitor'.


That's because AC is *not* defined by any change in direction,
but only by a rate of movement change.

Repeating yourself doesn't make you correct.

daestrom

"daestrom" wrote:
"Floyd L. Davidson" wrote in message
...
John Fields wrote:
On Sun, 12 Jun 2005 14:00:23 -0800, (Floyd L.
Davidson) wrote:

'Alternating' means both magnitude and direction vary over time. A current
that varies in magnitude but not direction is not 'alternating'.

Then you'll have a very difficult time explaining now a
transistor amplifier works if it uses AC coupling that involves
capacitors.

Since the voltage varies, the current will also, but the _direction_
in which the electrons are travelling will never change.

If it varies, it's AC.

Only by your apparent definition. But your definition does not agree with
the established industry.

Which industry? You can't do AC circuit analysis with any other
definition.

If there is such a think as "varying DC", connect a load to
it... through a capacitor. Now, how do you describe the effect
that load has on your "varying DC". The load see's *only* AC,
even according to your definition. That AC came from somewhere,
and it certainly was not generated by the capacitor.

By adding a capacitor in series, you have altered the circuit. The

Capacitors don't generate voltage or current. The circuit
alteration merely demonstrates that the voltage and current on
one side meets all of your requirements, while the identical
charge flow on the other side does not, which indicates a flaw
in your specification.

capacitor filters out the DC component of a the original varying DC voltage
applied.

Yes, which leaves the AC that was there all along. It's AC
after, and it was AC before. If you do circuit analysis the
treatment is exactly the same on both sides of the capacitor.

The capacitor has a varying DC voltage across it, but it never
changes polarity (you can use an electrolytic capacitor that is polarity
sensitive without damage).

Exactly. Yet there *is* current through the capacitor, which
only passes AC. That AC current isn't generated inside that
capacitor. It comes out one side, so it *had* to be coming in
the other side.

The current through the resulting series circuit *does* alternate in
magnitude and *direction*, even though the voltage applied to the circuit
varies in magnitude only. So yes, the 'AC came from somewhere'. But that
doesn't mean the applied voltage is AC. Such logic is flawed. There is no
'law of conservation of AC' that says it can't be 'generated by the
capacitor'.

That's hilarious. DC applied to a capacitor generates AC????

I don't think so.

That's because AC is *not* defined by any change in direction,
but only by a rate of movement change.

Repeating yourself doesn't make you correct.

Won't help your point either. And it makes no difference how many
places you find it ill defined either.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

On Sun, 12 Jun 2005 16:35:48 -0800, (Floyd L.
Davidson) wrote:

John Fields wrote:
On Sun, 12 Jun 2005 14:00:23 -0800, (Floyd L.
Davidson) wrote:

My point still stands, that if the current is changing, it is by
definition AC, and current not changing is DC. Trying to look
at it as DC is all in one direction and anything else is AC,
doesn't work.

---
Your point is flawed. Alternating Current, by definition, causes
electrons to move in one direction for a time, and then to reverse
direction for a time.

That isn't true.

---
Yes, it is. If you have proof, instead of just a statement to the
effect that it isn't, I'd love to see it.
---

The sinusoidally varying unipolar voltage under consideration _always_
forces electrons to move in one direction only.

A non-sequitor.

---
"Non sequitur." No. A non-sequitur is an inference or a conclusion
that does not follow from the premises, or a comment that is unrelated
to a preceding one. My error was the omission of a reference, Mr.
Lancaster's: "1 volt peak sinewave with a 0.6 volt dc term"
---

Since the voltage varies, the current will also, but the _direction_
in which the electrons are travelling will never change.

If it varies, it's AC.

---
No, it isn't. What's necessary is the polarity reversal before it can
be considered AC.
---

That means that the signal is DC. A varying DC, but DC nonetheless.

If there is such a think as "varying DC", connect a load to
it... through a capacitor. Now, how do you describe the effect
that load has on your "varying DC". The load see's *only* AC,
even according to your definition. That AC came from somewhere,
and it certainly was not generated by the capacitor.

---
It most certainly was!

Consider a DC coupled audio amplifier running from a single 12V
supply, with its output set to Vcc/2 and feeding an 8 ohm load with a
4VPP sinusoidal signal. Like this:

+12
|
+--o--+
| AMP |---+--Vout
+--o--+ |
| [4R]
| |
GND GND

Now, with phi being equal to the phase angle of the signal and zero
degrees corresponding the voltage halfway between the most positive
and least positive output voltage, the output voltage excursions will
look like this:

phi Vout
-----+------
0° 6V
90° 8V
180° 6V
270° 4V
360° 6V

Now, connect that magical capacitor between the amp and the load, as
shown below, and watch what happens:

+12
|
+--o--+
| AMP |---[cap]--+--Vout
+--o--+ |
| [4R]
| |
GND GND


phi Vout
-----+------
0° 0V
90° +2V
180° 0V
270° -2V
360° 0V

Why?

Well,for starters, consider that under quiescent conditions the
left-hand side of the cap will be charged to 6V and the right hand
side will be at zero volts since there is no galvanic path to the
output of the amp through the cap.

Now, imagine that the voltage at the amp's outout starts to go
positive. What will happen is that the amp will start sucking
electrons out of the cap, generating a potential difference across the
cap's plates which causes electrons to flow through the resistor,
making the top of the resistor more positive than the bottom.

Continuing in time, a point will be reached where the output of the
amp will start forcing electrons _into_ the resistor, at which point
the direction of travel of the electrons will be reversed. This
periodic reversal will cause the polarity of the signal into the
resistor to alternate. This alternating voltage will then give rise
to an _alternating current_ in the resistor.
---

That's because AC is *not* defined by any change in direction,
but only by a rate of movement change.

---
Poppycock. It's precisely the alternations in the direction of charge
flow which cause it to be called "Alternating Current".

Your way would have it be called AC by assigning some arbitrary rate
of change, irrespective of direction as the delineation point, which
makes no sense at all. That is, what would you specify as the rate of
change which would delineate between between AC and DC? 0.5A/s?
0.001A/s? 0.1V/s?

--
John Fields
Professional Circuit Designer

John Fields wrote:
On Sun, 12 Jun 2005 16:35:48 -0800, (Floyd L.
Davidson) wrote:
That means that the signal is DC. A varying DC, but DC nonetheless.

If there is such a think as "varying DC", connect a load to
it... through a capacitor. Now, how do you describe the effect
that load has on your "varying DC". The load see's *only* AC,
even according to your definition. That AC came from somewhere,
and it certainly was not generated by the capacitor.

---
It most certainly was!

Do a reality check on what you are saying! Capacitors do *not*
generate AC, and when the rest of your theory depends on the
idea that they do, you've made a mistake.

Consider a DC coupled audio amplifier running from a single 12V
supply, with its output set to Vcc/2 and feeding an 8 ohm load with a
4VPP sinusoidal signal. Like this:

+12
|
+--o--+
| AMP |---+--Vout
+--o--+ |
| [4R]
| |
GND GND

You haven't drawn the schematic of an amplifier. There is no
input. Call it what you like, but it isn't an amplifier.

Add the input, and then we know where the AC originated...

Now, with phi being equal to the phase angle of the signal and zero
degrees corresponding the voltage halfway between the most positive
and least positive output voltage, the output voltage excursions will
look like this:

phi Vout
-----+------
0° 6V
90° 8V
180° 6V
270° 4V
360° 6V

Clearly AC. (And if you don't treat it as AC, your circuit analysis
will be flawed.)

Now, connect that magical capacitor between the amp and the load, as
shown below, and watch what happens:

+12
|
+--o--+
| AMP |---[cap]--+--Vout
+--o--+ |
| [4R]
| |
GND GND

phi Vout
-----+------
0° 0V
90° +2V
180° 0V
270° -2V
360° 0V

Why?

Because you feed an AC signal to the capacitor, and hence you
see an AC signal on the other side.

What's your point? Capacitors pass AC and block DC. All you've
done is *prove* that there was AC coming out of the AMP (as well
as DC).

Well,for starters, consider that under quiescent conditions the
left-hand side of the cap will be charged to 6V and the right hand
side will be at zero volts since there is no galvanic path to the
output of the amp through the cap.

Now, imagine that the voltage at the amp's outout starts to go
positive. What will happen is that the amp will start sucking
electrons out of the cap, generating a potential difference across the
cap's plates which causes electrons to flow through the resistor,
making the top of the resistor more positive than the bottom.

And clearly you have an alternating voltage on both sides of the
capacitor, and an AC current passing through it. Not generated
by it, but passing through it.

Continuing in time, a point will be reached where the output of the
amp will start forcing electrons _into_ the resistor, at which point
the direction of travel of the electrons will be reversed. This
periodic reversal will cause the polarity of the signal into the
resistor to alternate. This alternating voltage will then give rise
to an _alternating current_ in the resistor.
---

That's because AC is *not* defined by any change in direction,
but only by a rate of movement change.

---
Poppycock. It's precisely the alternations in the direction of charge
flow which cause it to be called "Alternating Current".

It is defined by a differential (which necessarily will have a
sign reversal), not "polarity" reversals.

Your way would have it be called AC by assigning some arbitrary rate
of change, irrespective of direction as the delineation point, which
makes no sense at all. That is, what would you specify as the rate of
change which would delineate between between AC and DC? 0.5A/s?
0.001A/s? 0.1V/s?

*Any* rate of change (differential) that you can detect, means
you have detected AC.

There simply is no way to do circuit analysis with any other
definition.

Or do we really want three states:

A) DC

B) Varying DC[1]

C) AC[2]


[1] Varying DC is exactly like AC and all functions are
identical.

[2] AC is exactly like Varying DC and all functions are
identical.

That is 3 states in your mind, and only 2 in fact.

Not very reasonable from a logical point of view, but that is
exactly what we do have because of the historical baggage that
we carry along.

Remember when every electrical engineer would tell you that
current flows from the positive terminal of a battery to the
negative terminal... and every electronics engineer would tell
you that when the B battery is connected to a vacuum tube
circuit the current flows from the cathode to the anode. Of
course the positive battery terminal is connected to the anode,
so they can't both be correct.

Of course, then solid state electronics came along, and it became
clear that current wasn't even necessarily the movement of electrons,
but could also be the movement of a lack of electrons! How does
*that* fit your "polarity" requirements?

You are telling me the positive terminal supplies the current, and
the return path is to the negative terminal. I'm telling you that
electrons flow from the cathode to the anode, and I don't care how
many reference books you cite saying that current comes from the
positive terminal on that battery.

Same sort of historical baggage.


(And can the spelling flames. If you haven't got any better
manners than you do logic, you have no place complaining that I
forgot to run the spell check on that article. Your claim that
the referenced statement was not the non-sequitur that I pointed
out it was didn't hold water according to the very definition
*you* supplied!)

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

On Mon, 13 Jun 2005 07:37:08 -0800, (Floyd L.
Davidson) wrote:

John Fields wrote:
On Sun, 12 Jun 2005 16:35:48 -0800, (Floyd L.
Davidson) wrote:
That means that the signal is DC. A varying DC, but DC nonetheless.

If there is such a think as "varying DC", connect a load to
it... through a capacitor. Now, how do you describe the effect
that load has on your "varying DC". The load see's *only* AC,
even according to your definition. That AC came from somewhere,
and it certainly was not generated by the capacitor.

---
It most certainly was!

Do a reality check on what you are saying! Capacitors do *not*
generate AC, and when the rest of your theory depends on the
idea that they do, you've made a mistake.

---
Well, Floyd, Take a look at the schematics below and you may notice
that while the first one (the one without the cap in series with the
load) puts out a sinusoidally varying unipolar signal, (DC) the second
one (the one _with_ the cap in series with the load) puts out a
sinusoidally varying bipolar signal. (AC)

Now, since the only difference between them is the cap and one puts
out a varying DC signal while the other one puts out a true signal,
then the cap _must_ be generating the AC signal. If you have a
problem with 'generating' then perhaps 'converting' would be more to
your liking. I doubt it though, you seem to be in this only for the
argument and I'm sure you'll come up with reason why you're unhappy
with 'convert'.
---

Consider a DC coupled audio amplifier running from a single 12V
supply, with its output set to Vcc/2 and feeding an 8 ohm load with a
4VPP sinusoidal signal. Like this:

+12
|
+--o--+
| AMP |---+--Vout
+--o--+ |
| [4R]
| |
GND GND

You haven't drawn the schematic of an amplifier. There is no
input. Call it what you like, but it isn't an amplifier.

Add the input, and then we know where the AC originated...

---
LOL, you're grasping at straws!
I already said the amp was DC coupled, so showing an input isn't
necessary. But for you...

+12
|
+--o--+
INPUT---| AMP |---+--Vout
+--o--+ |
| [4R]
| |
GND GND

Assume a gain of 1.

Happy now?
---


Now, with phi being equal to the phase angle of the signal and zero
degrees corresponding the voltage halfway between the most positive
and least positive output voltage, the output voltage excursions will
look like this:

phi Vout
-----+------
0° 6V
90° 8V
180° 6V
270° 4V
360° 6V

Clearly AC. (And if you don't treat it as AC, your circuit analysis
will be flawed.)

---
You seem to want to put the cart before the horse in that you're
spouting 'circuit analysis' before you've gotten a grasp of the
basics. But if you want to play that way, OK. It's clearly a
fluctuating DC signal, and if you don't take that _fact_ into
consideration _your_ circuit analysis will be erroneous.
---

Now, connect that magical capacitor between the amp and the load, as
shown below, and watch what happens:

+12
|
+--o--+
| AMP |---[cap]--+--Vout
+--o--+ |
| [4R]
| |
GND GND

phi Vout
-----+------
0° 0V
90° +2V
180° 0V
270° -2V
360° 0V

Why?

Because you feed an AC signal to the capacitor, and hence you
see an AC signal on the other side.

---
No, look a little more closely and you'll see (well, maybe...) that
the current on the input side never changed direction (remained DC),
while the current into the load alternated between going into the load
and coming out of the load. IOW, it went into the cap as fluctuating
DC and came out AC.
---

What's your point? Capacitors pass AC and block DC. All you've
done is *prove* that there was AC coming out of the AMP (as well
as DC).

---
No, there was _no_ AC coming out of the amp, (no changes in the
direction of charge flow, only changes in the magnitude) just
fluctuating DC which the cap converted into AC.
---

Well,for starters, consider that under quiescent conditions the
left-hand side of the cap will be charged to 6V and the right hand
side will be at zero volts since there is no galvanic path to the
output of the amp through the cap.

Now, imagine that the voltage at the amp's outout starts to go
positive. What will happen is that the amp will start sucking
electrons out of the cap, generating a potential difference across the
cap's plates which causes electrons to flow through the resistor,
making the top of the resistor more positive than the bottom.

And clearly you have an alternating voltage on both sides of the
capacitor, and an AC current passing through it. Not generated
by it, but passing through it.

---
No, there is a fluctuating DC on the input side of the cap which the
cap converts to AC to present to the load.
---

Continuing in time, a point will be reached where the output of the
amp will start forcing electrons _into_ the resistor, at which point
the direction of travel of the electrons will be reversed. This
periodic reversal will cause the polarity of the signal into the
resistor to alternate. This alternating voltage will then give rise
to an _alternating current_ in the resistor.
---

That's because AC is *not* defined by any change in direction,
but only by a rate of movement change.

---
Poppycock. It's precisely the alternations in the direction of charge
flow which cause it to be called "Alternating Current".

It is defined by a differential (which necessarily will have a
sign reversal), not "polarity" reversals.

---
Specious gobbledygook.

A reversal of sign is, by definition, a reversal of polarity.
---

Your way would have it be called AC by assigning some arbitrary rate
of change, irrespective of direction as the delineation point, which
makes no sense at all. That is, what would you specify as the rate of
change which would delineate between between AC and DC? 0.5A/s?
0.001A/s? 0.1V/s?

*Any* rate of change (differential) that you can detect, means
you have detected AC.

---
Only if it's accompanied by a change in the direction of charge flow.
---

..
.. Snipped a lot of irrelevant trash apparently designed to change the
.. subject.
..

(And can the spelling flames. If you haven't got any better
manners than you do logic, you have no place complaining that I
forgot to run the spell check on that article. Your claim that
the referenced statement was not the non-sequitur that I pointed
out it was didn't hold water according to the very definition
*you* supplied!)

---
The point is that you didn't point out a non sequitur. (notice that
there's no apostrophe in there) The definition, which I got from
Webster's College Dictionary and posted for your edification, should
have made that clear.

And, speaking of manners, I suggest that yours need a little trip past
Emily Post.




--
John Fields
Professional Circuit Designer

On Sun, 12 Jun 2005 14:00:23 -0800, (Floyd L.
Davidson) wrote:


Put an ammeter there and it says zero. That's zero. Electrons bouncing
around in the conductor have an average net displacement, over time, of 0.

Is this an AC ammeter, or a DC ammeter? (And isn't that just a voltmeter
anyway, in most actual cases????) Hmmm...

---
No. With the exception of electroscopes and such like, all voltmeters
are really ammmeters and what was being referred to was really a
galvanometer
---

--
John Fields
Professional Circuit Designer