Kitchen Man wrote:
On Sun, 12 Jun 2005 14:33:39 -0500, John Fields
wrote:


On 12 Jun 2005 09:01:11 -0700, wrote:


It's a shame you have to weed thru all the crap from some
of the posters here who have a lot of time on their hands and
have no tolerance for those who are just learning their craft....

---
It's a shame that those of us who give of our time in an effort to
edify the ignorant are often abused by imbeciles who can't take
correction gracefully.


It is equally a shame that there are those that are sometimes
incapable of offering correction gracefully, eh, John? If it pains
you so much to engage in your ungracious edifying, perhaps you would
do well to bugger off, and leave the stress of educating imbeciles to
those with more patience.


Interesting! I thought John's response to the op was
called for. The OP is going to get himself into trouble
with the attitutde he's exhibited. In my opinion, John
saw through the BS and called a spade a spade. I don't
know whether the OP got it or not - but John made it
clear that the BS wasn't fooling anybody.

I'll have to go back and read it again in light of
your post.

Ed

"Don Lancaster" wrote in message
...

"AC" or "DC" are gross and meaningless oversimplifications.

True but pointless. We know what we mean. Even 'current' is a borrowed term
used as an analogy as is 'potential' or even 'pressure'. If we have voltage
surely we should only speak of amperage.

N

On Sun, 12 Jun 2005 16:50:51 -0500, John Fields
wrote:

On Sun, 12 Jun 2005 13:39:22 -0700, Kitchen Man
wrote:

On 10 Jun 2005 23:06:10 -0700, wrote:

You actually proved my
point that DC is DEFINED (i.e. by convention) as "zero frequency".
Is it that weird to posit that the superior concept with respect to
considering any signal as AC or DC, be the actual NET current flow? I
could see your point if signals were classified as either "ZF" ("zero
frequency") or "NZF" (non-zero frequency") but we are dealing with "DC"
or "AC"

If nothing else, your stubborn adherence to a flawed terminology and
lack of openness to furthering your understanding will make you look
like an idiot in a job interview, should you ever decide to pursue
career advancement in the electronics industry. Please note that I am
not saying you are an idiot, just that you will look like one in an
interview. The interviewers will assume you know very little about
the basics of the craft if you carry on like this, or at the very
least will see you as a detriment to teamwork. HTH.

---
His attitude, if he persists with it, will be a serious detriment no
matter what field of endeavor he chooses to enter.

Oh, I agree. I just think it helps to be a bit patient. Not that I'm
all that good at patience, myself. But we should try. We have all
been rookies, once or twice.

Starting to see it my way, Al?-)

--
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

Don Lancaster wrote:
Floyd L. Davidson wrote:
Don Lancaster wrote:

DC, of course, cannot exist at all ever. Because it would have
to be unvarying through infinite time.


Boy, you are *pedantic*!

Can't we just define DC as current that doesn't vary "much"
for at last a "long" time. Granted that is ambiguous, but
what else would we the argue about, weather?


No.

Sum a 1 volt peak sinewave with a 0.6 volt dc term and you have a
waveform whose polarity continuously changes but whose average value
is continuous.

Looking at the Fourier terms makes this waveform perfectly clear.
Calling it "AC" or "DC" does not.

"AC" or "DC" are gross and meaningless oversimplifications.

That's going a bit far. "Meaningless" means no meaning, and that is not
really an accurate description for the terms AC and DC. They have a
pretty well understood meaning, despite some suggestions in this thread.

"quotes with no meaning, are meaningless" - Kevin Aylward


Kevin Aylward

http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

Floyd L. Davidson wrote:
Bob Penoyer wrote:
On Sat, 11 Jun 2005 10:36:54 -0400, "Tam/WB2TT"
wrote:

snip

Yes. DC by definition is zero frequency.

Um, no. DC is Direct Current, i.e., current that flows in one
direction. For example, the output from a rectifier is DC but it
certainly isn't "zero frequency."

Actually, DC from a rectifier *is* "zero frequency", to the
degree that it is DC. Of course until the AC is filtered out,
it has both AC and DC components.

The output of a rectifier contains both AC and DC. You put a filter
on it to get close to pure DC.

That is *precisely* correct. (It just doesn't tell enough of
the story to explain the confusion of this "flows in one
direction" definition of DC.)

A rectified AC waveform contains DC and AC components but if the
current isn't changing direction, it isn't alternating current. And,
if it isn't AC, it's DC.

The output of a rectifier until filtered *does* have both AC and
DC, which actually is another way of saying that yes it *does*
change directions.

What? you say!

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:

Since we are quibbling her on terms, lets get this bit straight shall
we.

"Current flow" is wrong. Its simply "current" or "charge flow".
"Current" already contains the notion of "flow".


Kevin Aylward

http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

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

"Floyd L. Davidson" wrote in message
...
John Fields wrote:
On Sun, 12 Jun 2005 17:15:06 -0700, Don Lancaster
wrote:

Sum a 1 volt peak sinewave with a 0.6 volt dc term and you have a
waveform whose polarity continuously changes but whose average value is
continuous.

---
No, you have a waveform with a polarity which changes _periodically_,
making it an AC signal. Do the electrons traversing the circuit
change direction? Yes. Do the electrons in a DC circuit ever change
direction? No.

Ergo, because of the periodic polarity reversals what you're looking
at is AC.

And, according to what you've said in other posts, if that were a
0.6 volt peak sinewave with 1.0 volt dc, it wouldn't be.

But your definition of AC is faulty, because in fact they are the
same thing, and *both* of them contain an AC component and a DC
component, even if the general direction of electrons is always the
same.

No, both do not - only one of the 1 volt/.6 volt examples given has an
_alternating_ direction component - both examples do have a _variation_ in
their magnitude component.
( This is not a new discussion - and all of the dozen or so engineering
and physics texts and training manuals I have researched on the matter
adhere to the "alternating is reversing" definition of AC. It has been
custom and practice for at least 40 years.)

1) the 1 volt dc with the .6 sine variation does not alternate its
direction of flow. Its flow only varies in the magnitude of the charge
flowing always in one direction.
It has no alternating current ( i.e, it has no regularly reversing, i.e.
_alternating_, charge flow direction)

2) the 1 volt sinewave with the .6 volt dc does reverse charge flow
direction. It is alternating in its flow direction.
It also varies in its magnitude.

The direction of the description vector must alternate in order to have
Alternating Current. If it does not change direction but only varies in
magnitude, the descriptive vector is not alternating, it is merely varying
in magnitude.

3) Impedance laws apply equally to varying DC and to AC.


---

Looking at the Fourier terms makes this waveform perfectly clear.
Calling it "AC" or "DC" does not.

---
Why go there? Your description was adequate to indicate that polarity
reversals occur, therefore making the signal voltage alternate between
two different polarities, therefore making the current alternate
between polarities as well. That's why it's called "Alternating
Current".

Except, polarity reversals are not significant to the definition
of AC.

---

"AC" or "DC" are gross and meaningless oversimplifications.

---
Uh-huh...

He's right.

--
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

"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)

"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)

"Kevin Aylward" wrote:
Don Lancaster wrote:
"AC" or "DC" are gross and meaningless oversimplifications.

That's going a bit far. "Meaningless" means no meaning, and that is not
really an accurate description for the terms AC and DC. They have a
pretty well understood meaning, despite some suggestions in this thread.

Given the significant experience of several people involved in
this discussion, and the wide variety of interpretations they
are giving to those terms, it would seem that just about the
*only* thing one could positively take away from this particular
discussion is that, as Don says, those terms are meaningless.

--
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:


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

"--" wrote:
"Floyd L. Davidson" wrote:
John Fields wrote:
On Sun, 12 Jun 2005 17:15:06 -0700, Don Lancaster
wrote:

Sum a 1 volt peak sinewave with a 0.6 volt dc term and you have a
waveform whose polarity continuously changes but whose average value is
continuous.

---
No, you have a waveform with a polarity which changes _periodically_,
making it an AC signal. Do the electrons traversing the circuit
change direction? Yes. Do the electrons in a DC circuit ever change
direction? No.

Ergo, because of the periodic polarity reversals what you're looking
at is AC.

And, according to what you've said in other posts, if that were a
0.6 volt peak sinewave with 1.0 volt dc, it wouldn't be.

But your definition of AC is faulty, because in fact they are the
same thing, and *both* of them contain an AC component and a DC
component, even if the general direction of electrons is always the
same.

No, both do not - only one of the 1 volt/.6 volt examples given has an
_alternating_ direction component - both examples do have a _variation_ in
their magnitude component.
( This is not a new discussion - and all of the dozen or so engineering
and physics texts and training manuals I have researched on the matter
adhere to the "alternating is reversing" definition of AC. It has been
custom and practice for at least 40 years.)

1) the 1 volt dc with the .6 sine variation does not alternate its
direction of flow. Its flow only varies in the magnitude of the charge
flowing always in one direction.
It has no alternating current ( i.e, it has no regularly reversing, i.e.
_alternating_, charge flow direction)

2) the 1 volt sinewave with the .6 volt dc does reverse charge flow
direction. It is alternating in its flow direction.
It also varies in its magnitude.

The direction of the description vector must alternate in order to have
Alternating Current. If it does not change direction but only varies in
magnitude, the descriptive vector is not alternating, it is merely varying
in magnitude.

3) Impedance laws apply equally to varying DC and to AC.

Item 3 is correct. That is because "varying DC" *is* AC.

It is AC even if the axis is shifted far enough to avoid
polarity reversals relative only to some specifically defined 0
current.

The reversals are relative... to the steady state condition,
not to some magical 0 current where supposedly no electrons are
flowing.

Otherwise, instead of two types, you are dividing circuit analysis
into three types, two of which are identical in all significant
respects other than an arbitrary definition that is meaningless.

It makes no sense to say that "Impedance laws apply equally" and
then claim that the two are not identical.

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

NSM wrote:

"Choreboy" wrote in message
...

To call a waveform an AC sine wave implies that there is no DC, but this
thread is the first time I've read the claim that all sine waves are AC
sine waves.

FWIW, most waveforms can be created as the sum of sine waves. I wrote an
interesting computer demo once that showed how a sine and it's harmonics
could be added graphically to form a better and better approximation of a
square wave, running through what looked like Butterworth etc. responses.

N

With high frequency and amplitude, a sine wave could be very steep at 0
and 180 degrees. It could also turn sharply at 90 and 270, like the
corner of a square wave. You would need low frequency and amplitude for
a sine wave to approximate the flat peaks of a square wave.

That part is simple enough for me, but I don't understand harmonics. If
you overdrive an amplifier with a sine wave, the output will resemble a
square wave. I know the output can be broken down into the input
frequency and its odd multiples. I'll have to accept it on faith.

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

Strictly speaking, I believe the reactance (part of impedance)
equations apply to any variation in current magnitude. Their appropriate
application does not in any way require reversing the charge.

1) I think one needs to define the term "alternating current" by its
phenomena rather than define it by what applies to "AC". In other words,
define AC as alternating current -rather than defining AC as "anything
requiring an impedance calculation because of its magnitude variation".
( OK, all scientific definitions require definitions in terms of other
defined concepts; thus voltage and charge are defined in terms of force.
And yes, any phenomena in its purest defined form uses the fewest of the
core units, and only the core units, of the measuring system. And yes,
since, unlike in the British ft-sec-lb system, force is not a core unit of
the metric kg-sec-m system, one cannot be as "pure" in the metric system
with many definitions as one can be in the British system, "decile"
convenience notwithstanding)

2) There are two phenomena and two descriptive words if one uses the
mathematical description of the changes associated with current: changes in
current _direction_ and changes in current _magnitude_.

There are three (or more) phenomena if one uses only the two descriptive
terms _AC_ and _DC_, well evidenced in this thread: changes in direction and
magnitude, changes in magnitude only, or no changes in either magnitude or
direction. Three phenomena defined using only two words for those three
cannot be specific and exclusive enough for a rigorous definition. The
middle condition, the overlap as it were, ends up wanting.

3) In the definition approach to a phenomena, one deals with the
descriptive term and the phenomena itself and ignores the present attached
effects. Once the definition is had, then the phenomena's interaction with
other phenomena can be determined. Yes, having such rigor in a definition
can be more complicated in its application.

In the application approach to defining a phenomena, one defines by
addressing what equations, etc., apply to the condition. In this approach,
you end up in circular arguments, chasing your tail. Something always will
not fit. Like changes in magnitude without changes in direction.


"Floyd L. Davidson" wrote in message
...
"--" wrote:
"Floyd L. Davidson" wrote:
John Fields wrote:
On Sun, 12 Jun 2005 17:15:06 -0700, Don Lancaster
wrote:

Sum a 1 volt peak sinewave with a 0.6 volt dc term and you have a
waveform whose polarity continuously changes but whose average value
is
continuous.

---
No, you have a waveform with a polarity which changes _periodically_,
making it an AC signal. Do the electrons traversing the circuit
change direction? Yes. Do the electrons in a DC circuit ever change
direction? No.

Ergo, because of the periodic polarity reversals what you're looking
at is AC.

And, according to what you've said in other posts, if that were a
0.6 volt peak sinewave with 1.0 volt dc, it wouldn't be.

But your definition of AC is faulty, because in fact they are the
same thing, and *both* of them contain an AC component and a DC
component, even if the general direction of electrons is always the
same.

No, both do not - only one of the 1 volt/.6 volt examples given has an
_alternating_ direction component - both examples do have a _variation_
in
their magnitude component.
( This is not a new discussion - and all of the dozen or so engineering
and physics texts and training manuals I have researched on the matter
adhere to the "alternating is reversing" definition of AC. It has been
custom and practice for at least 40 years.)

1) the 1 volt dc with the .6 sine variation does not alternate its
direction of flow. Its flow only varies in the magnitude of the charge
flowing always in one direction.
It has no alternating current ( i.e, it has no regularly reversing,
i.e.
_alternating_, charge flow direction)

2) the 1 volt sinewave with the .6 volt dc does reverse charge flow
direction. It is alternating in its flow direction.
It also varies in its magnitude.

The direction of the description vector must alternate in order to have
Alternating Current. If it does not change direction but only varies in
magnitude, the descriptive vector is not alternating, it is merely
varying
in magnitude.

3) Impedance laws apply equally to varying DC and to AC.

Item 3 is correct. That is because "varying DC" *is* AC.

It is AC even if the axis is shifted far enough to avoid
polarity reversals relative only to some specifically defined 0
current.

The reversals are relative... to the steady state condition,
not to some magical 0 current where supposedly no electrons are
flowing.

Otherwise, instead of two types, you are dividing circuit analysis
into three types, two of which are identical in all significant
respects other than an arbitrary definition that is meaningless.

It makes no sense to say that "Impedance laws apply equally" and
then claim that the two are not identical.

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

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

The freezing point and boiling point of water are both have
a clearly defined intrinsic meaning to a chemist. "DC sine wave"
is a non-sequiter. It's a made-up self-contradictory term
that won't have an unambiguous meaning to anybody who knows
electronics, no matter how clear it is to you.

wrote:
Go back to the original few posts to see how it got started....despite
being explicit about the specs of the wave, someone childishly objected
to my casual usage of "DC sine wave".....would it have been
objectionable had I used "a fully DC-offset sine wave"?......again,
I've never claimed that I was using "official" or
conventionally-correct teminology or nomenclature....I just really
object that anyone would object to what I was saying, when its meaning
was explicitly stated (using actual numbers) and the phrase "fully DC
sine wave", although conventionly queer, is not at all cryptic or hard
to figure out......if I were a chemist and someone said "200 degrees
above the freezing point of water", I wouldn't mock them, just
respectfully point out that it's more common to say "20 degrees above
the boiling point of water".....I would consider the person ignorant of
the conventional terminology, but I would consider the person dead-on
if he were talking about 232 degrees F.

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)

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)

"--" wrote:
Strictly speaking, I believe the reactance (part of impedance)
equations apply to any variation in current magnitude. Their appropriate
application does not in any way require reversing the charge.

Exactly.

1) I think one needs to define the term "alternating current" by its
phenomena rather than define it by what applies to "AC". In other words,
define AC as alternating current -rather than defining AC as "anything
requiring an impedance calculation because of its magnitude variation".

What value does that have? The problem is circuit analysis,
which requires the division between DC and AC, and the only
division that makes sense is between non-changing current and
changing current.

3) In the definition approach to a phenomena, one deals with the
descriptive term and the phenomena itself and ignores the present attached

The problem is defining something with no practical value. If
AC is a changing current, that includes changing polarity, and
covers the actual significant difference from DC. If AC is
defined only as changing polarity, we also have to have an
entire separate set of identical functions and definitions, one
for "varying DC" and one for "AC". Since the analysis is the
same, there is no point in separation of the two.

And "varying DC" is a contradiction in terms to begin with. Do
we actually need *four* states:

1 -- DC
2 -- Varying DC
3 -- AC
4 -- Steady AC

Boy, that should may first year text books *really* interesting!

Either that or we are back to Don Lancaster's correct statement
that they are meaningless terms anyway. They certainly are if
that is the way they are defined!

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

Choreboy wrote:

With high frequency and amplitude, a sine wave could be very steep at 0
and 180 degrees. It could also turn sharply at 90 and 270, like the
corner of a square wave. You would need low frequency and amplitude for
a sine wave to approximate the flat peaks of a square wave.

That part is simple enough for me, but I don't understand harmonics. If
you overdrive an amplifier with a sine wave, the output will resemble a
square wave. I know the output can be broken down into the input
frequency and its odd multiples. I'll have to accept it on faith.

You might want to look into the basis of Fourier analysis. It all
falls out of a very simple mathematical property of the sine wave.

If you take any periodic waveform, and multiply its value at every
point in time with the value of any frequency of sine wave at the same
points in time, over all time and add up (integrate) all the products
and divide by the total time (an infinite amount of time), only sine
waves that fit an integral number of cycles within the period of the
waveform will produce nonzero results (infinite integral divided by
infinite time). In fact, it can be shown that you get the same
quotient for harmonics if you use any integral number of periods of
the waveform, including one period. Testing an infinite number of
waves is only necessary to show that non harmonics always produce a
zero contribution. For instance, if you test a sine wave that fits
1.000001 cycles into a cycle of the waveform, you don't reach the
first zero result till you include a million periods of the waveform
(and you get more zeros at every integer multiple of a million cycles,
with a smaller and smaller cycle of results between those millions as
the number of cycles increases because you are dividing by larger and
larger times).

Harmonics (sine waves that fit an integral number of cycles within the
waveform) will produce a finite result representing that frequencies
contribution to the waveform. (Actually you have to test both the
sine and cosine against the waveform to cover all possible phase
shifted versions of the sine. Any phase shifted sine can be broken
sown into sine and cosine components. Another nice property of sine
waves.) Since only harmonics contribute to the total wave shape, you
can skip all the other frequencies, and just evaluate the part each
harmonic contributes to making the total waveform.

That is Fourier analysis.

The rest is about making the math more efficient.

On Mon, 13 Jun 2005 07:58:46 -0800, (Floyd L.
Davidson) wrote:

*Snip*

Either that or we are back to Don Lancaster's correct statement
that they are meaningless terms anyway. They certainly are if
that is the way they are defined!

Don first said:
---------------------------------------
'"DC" is simply the first (or "offset" term in the Fourier expression
of
any repetitive waveform.

"AC" are all of the remaining components.'
----------------------------------------

Then he said:
----------------------------------------
'"AC" or "DC" are gross and meaningless oversimplifications.'
----------------------------------------

Which are we to believe?

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 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.

"Floyd L. Davidson" wrote in message
...
"--" wrote:
Strictly speaking, I believe the reactance (part of impedance)
equations apply to any variation in current magnitude. Their appropriate
application does not in any way require reversing the charge.

Exactly.

1) I think one needs to define the term "alternating current" by its
phenomena rather than define it by what applies to "AC". In other
words,
define AC as alternating current -rather than defining AC as "anything
requiring an impedance calculation because of its magnitude variation".

What value does that have? The problem is circuit analysis,

No, rather the problem is that many of the fundamental physical sciences and
most of electrical engineering use the concept, and it is not used merely by
a small corner of circuit analysis. The definition has to work for all the
sciences where it may be used.
E.g., many switches use the "AC as reversing" concept for quenching
contact arcs during switching (as the current passes thru zero as direction
reverses) and the defintion of AC as varying DC falls flat for that purpose.
Install an AC designed switch on a varying DC circuit, and you may well have
a safety switch contacts welded shut. Here, AC DEFINITELY means reversing
direction.

which requires the division between DC and AC,

I believe the equations are not DC-AC specific - the "AC" term drops to
zero if the change in magnitude drops to zero. Your rationale of using the
equations does not hold up.

and the only
division that makes sense is between non-changing current and
changing current.


changing in direction or magnitude?

You suggest we use AC is defined as:
"regularly or irregularly varying uni- or bi- directional current if it
varies at a frequency that could have an effect for that application; unless
it is digital, where then the one-time rise time and the fall time of each
state change is calculated as AC, too, even though it 'alternates' once for
each pulse"

vs.

AC is defined as:

charge flow that changes direction.


which leaves the calculations for reactance out of the definition.

3) In the definition approach to a phenomena, one deals with the
descriptive term and the phenomena itself and ignores the present
attached

The problem is defining something with no practical value.

We define air, and black holes, and impracticality.
The circular logic that has your AC/DC missing half the paramters of the
phenomena also has no use for defining air since we only feel wind, for not
defining black holes which have no practical value since we have never seen
one, and no use for the definition of impracticality because by definition
it has no practical value.

If
AC is a changing current, that includes changing polarity, and
covers the actual significant difference from DC. If AC is
defined only as changing polarity, we also have to have an
entire separate set of identical functions and definitions, one
for "varying DC" and one for "AC".

not if we consider the two paramters that make up the phenomena - direction
and magnitude.
And if memory serves me correctly, the "AC" equations are rigorous, and
apply equally well to your one-voltage DC when the frequerncy drops to zero-
the reactance term of the changing magnitude goes to zero.

Since the analysis is the
same, there is no point in separation of the two.

And "varying DC" is a contradiction in terms to begin with. Do
we actually need *four* states:

1 -- DC
2 -- Varying DC
3 -- AC
4 -- Steady AC

no, just two - reversing flow direction, and varying magnitude.

Because the reactance equations only apply to varying magnitude, and they do
not apply to reversing direction.


Boy, that should may first year text books *really* interesting!

Either that or we are back to Don Lancaster's correct statement
that they are meaningless terms anyway. They certainly are if
that is the way they are defined!

If one has never heard of the ocean, one finds the ocean meaningless.
And for the memebrs of that society, they also would find ocean-going
boats useless. because they have to define the ocean thru their own
experience.
As I understood, scienctific method is designed to remove personal views
from science. Thus the definition,must stand alone, and since we can't see
all that is ahead, science has to fall in behind a definition of that
phenomena in pure terms.

imho.......

----------------

Alternating-direction Current, aka Alternating Current

Direction-specific Current, aka Direct Current.



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

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

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

Reality check! Capacitors are passive devices. They do *NOT*
generate signals.

All that has happened is the capacitor does not pass DC. You
haven't generated AC on one side, you've merely removed the DC.

I don't see how that could be any more obvious. You did take
a high school physics class, didn't you? *Use* what you learned!

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.

Okay, so you not only need to restudy high school physics, but
differential equations too.

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.

If you had read the definition you posted, you might have
noticed that it perfectly described the remark that I was
commenting on. It had nothing to do with the discussion.

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

You are the one stooping to spelling flames.

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

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

Oh, my. And you said what about Emily Post.

Nothing I said was a flame. And I'd suggest you go practice (a *lot*)
before you try me on for a flame war. Especially if you think *that*
is a flame.

I'm starting to think you're having a real problem with reading
comprehension.

Apparently I read a lot better than you write.

I write that for the current in a load to alternate,

You write a lot of things that are not valid.

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

Do you understand that is not significant? The reactance of circuit
components, the fundamental significance of AC circuit analysis, does
not depend upon polarity alternation in any way. What else is there
to talk about? How many chocolate drops should be in each chocolate
chip cookie? I await your essay on *something* of significance.

But please, that is the *end* of discussion on your confusion about
AC.


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

John Popelish wrote:

Choreboy wrote:

With high frequency and amplitude, a sine wave could be very steep at 0
and 180 degrees. It could also turn sharply at 90 and 270, like the
corner of a square wave. You would need low frequency and amplitude for
a sine wave to approximate the flat peaks of a square wave.

That part is simple enough for me, but I don't understand harmonics. If
you overdrive an amplifier with a sine wave, the output will resemble a
square wave. I know the output can be broken down into the input
frequency and its odd multiples. I'll have to accept it on faith.

You might want to look into the basis of Fourier analysis. It all
falls out of a very simple mathematical property of the sine wave.

If you take any periodic waveform, and multiply its value at every
point in time with the value of any frequency of sine wave at the same
points in time, over all time and add up (integrate) all the products
and divide by the total time (an infinite amount of time), only sine
waves that fit an integral number of cycles within the period of the
waveform will produce nonzero results (infinite integral divided by
infinite time). In fact, it can be shown that you get the same
quotient for harmonics if you use any integral number of periods of
the waveform, including one period. Testing an infinite number of
waves is only necessary to show that non harmonics always produce a
zero contribution. For instance, if you test a sine wave that fits
1.000001 cycles into a cycle of the waveform, you don't reach the
first zero result till you include a million periods of the waveform
(and you get more zeros at every integer multiple of a million cycles,
with a smaller and smaller cycle of results between those millions as
the number of cycles increases because you are dividing by larger and
larger times).

Harmonics (sine waves that fit an integral number of cycles within the
waveform) will produce a finite result representing that frequencies
contribution to the waveform. (Actually you have to test both the
sine and cosine against the waveform to cover all possible phase
shifted versions of the sine. Any phase shifted sine can be broken
sown into sine and cosine components. Another nice property of sine
waves.) Since only harmonics contribute to the total wave shape, you
can skip all the other frequencies, and just evaluate the part each
harmonic contributes to making the total waveform.

That is Fourier analysis.

The rest is about making the math more efficient.

That's easy for you to say!

I think you've shown me something. When I hear "sine wave" I imagine
one cycle. I guess that's wrong, and a wave is a train of cycles.

Musical harmony is in a sustained interaction between trains of cycles.
The interaction won't be simple enough to hear unless the quotient
between the frequencies is a small integer.

When they talk about harmonics in an electrical wave, I guess they're
talking about the potential for energy transfer. In that case, only odd
multiples of the fundamental will stay in phase to tap the energy from
the distortion. Where a wave is flattened it may resemble part of a
sine curve with a longer period than the fundamental, but that doesn't
count because you can't tap energy from the flat part.

If there's any truth in what I've said, I'll forget in a flash. In 1975
I was working in a repair facility. We'd use Bird Wattmeters to see
forward and reflected power in antenna feeds. We knew the jargon and
how to use the meters, but one day it struck me that none of us
understood why they worked. I had a flash of insight and everybody
stopped work to listen to me explain. Their faces lit up with
comprehension. I felt pretty smart. The next day I couldn't remember
whatever it was I'd figured out.

The Phantom wrote:
On Mon, 13 Jun 2005 07:58:46 -0800, (Floyd L.
Davidson) wrote:

*Snip*

Either that or we are back to Don Lancaster's correct statement
that they are meaningless terms anyway. They certainly are if
that is the way they are defined!

Don first said:
---------------------------------------
'"DC" is simply the first (or "offset" term in the Fourier expression
of
any repetitive waveform.

"AC" are all of the remaining components.'
----------------------------------------

Then he said:
----------------------------------------
'"AC" or "DC" are gross and meaningless oversimplifications.'
----------------------------------------

Which are we to believe?

There is no contradiction, so what is wrong with understanding both
statements?

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

"--" wrote:
"Floyd L. Davidson" wrote:
"--" wrote:
Strictly speaking, I believe the reactance (part of impedance)
equations apply to any variation in current magnitude. Their appropriate
application does not in any way require reversing the charge.

Exactly.

1) I think one needs to define the term "alternating current" by its
phenomena rather than define it by what applies to "AC". In other
words,
define AC as alternating current -rather than defining AC as "anything
requiring an impedance calculation because of its magnitude variation".

What value does that have? The problem is circuit analysis,

No, rather the problem is that many of the fundamental physical sciences and
most of electrical engineering use the concept, and it is not used merely by
a small corner of circuit analysis. The definition has to work for all the
sciences where it may be used.
E.g., many switches use the "AC as reversing" concept for quenching
contact arcs during switching (as the current passes thru zero as direction
reverses) and the defintion of AC as varying DC falls flat for that purpose.
Install an AC designed switch on a varying DC circuit, and you may well have
a safety switch contacts welded shut. Here, AC DEFINITELY means reversing
direction.

Bad example. That does *not* require a direction reversal. All
it requires is understanding that it is relative to the static
state.

It does happen that the static state in that specific case is
when a polarity reversal takes place, but in the general case it
is not required. In other examples both sides of the switch
might well be at some DC potential, that happens to be equal on
both sides at the time the switch is made, even though there is
no direction reversal.

which requires the division between DC and AC,

I believe the equations are not DC-AC specific - the "AC" term drops to
zero if the change in magnitude drops to zero. Your rationale of using the
equations does not hold up.

Everything concerned with reactance is AC specific. Nothing
concerned with reactance requires a polarity reversal.
Reactance is the essence of the difference between DC and AC,
not some notion of reversing polarity.

AC is defined as:

charge flow that changes direction.

which leaves the calculations for reactance out of the definition.

Which means it is worthless. Reactance *is* the significance.

3) In the definition approach to a phenomena, one deals with the
descriptive term and the phenomena itself and ignores the present
attached

The problem is defining something with no practical value.

We define air, and black holes, and impracticality.

All of which *does* have practical value.

And if memory serves me correctly, the "AC" equations are rigorous, and
apply equally well to your one-voltage DC when the frequerncy drops to zero-
the reactance term of the changing magnitude goes to zero.

That is an hilarious idea! If the magnitude is zero all the way
around... we aren't talking about AC or DC... maybe about
blown breakers or taking a coffee break, but not about current.

And "varying DC" is a contradiction in terms to begin with. Do
we actually need *four* states:

1 -- DC
2 -- Varying DC
3 -- AC
4 -- Steady AC

no, just two - reversing flow direction, and varying magnitude.

Oh? DC doesn't exist? What about "steady AC"? (That's two
exactly equal signals 180 degrees out of phase, combined in that
capacitor which can generate AC mentioned by John Fields,
perhaps???)

Because the reactance equations only apply to varying magnitude, and they do
not apply to reversing direction.

Then why would we be concerned at all about this reversing
direction, and give it a specific name and have a whole separate
field of study for it? Sounds like we need to be concerned with
varying magnitude, *not* with reversing direction. (Which is
what I've been saying...)

As I understood, scienctific method is designed to remove personal views
from science. Thus the definition,must stand alone, and since we can't see
all that is ahead, science has to fall in behind a definition of that
phenomena in pure terms.

imho.......

A nice goal.

----------------

Alternating-direction Current, aka Alternating Current

Except that alternating direction has no significance. Changing
magnitude does. Why bother with alternating-direction at all,
it is just an insignificant, though interesting, part of the
more general case of changing magnitude. All of the same
equations apply.

Direction-specific Current, aka Direct Current.

And if you claim that only alternating direction current is AC,
then you have to have two sets of equations for DC, one for
non-varying magnitude and one for varying magnitude.

That doesn't make a lick of sense.

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

Choreboy wrote:
John Popelish wrote:
(snip)

That is Fourier analysis.

The rest is about making the math more efficient.


That's easy for you to say!

I think you've shown me something. When I hear "sine wave" I imagine
one cycle. I guess that's wrong, and a wave is a train of cycles.

True mathematical sine waves extend from infinite negative time to
infinite positive time. Practical sine waves last long enough for
things to respond to their frequency. How long that is, depends o
what is reacting to it. A frequency counter operating in period mode
needs only a single cycle to make its measurement. An ear needs
several cycles to several dozen cycles, depending on exactly what part
of the audible spectrum being detected (this property of ears is part
o the MP3 music encoding scheme). A quartz lattice filter may need
thousands of cycles to of a pure frequency before it develops a nearly
steady state output.

Musical harmony is in a sustained interaction between trains of cycles.
The interaction won't be simple enough to hear unless the quotient
between the frequencies is a small integer.

Something like that. Each frequency component in the signal has to
last long enough for the time response of that frequency of the ear's
sorting system to respond to it. If two frequencies fall within a
single reception band, they are not heard as two tones, but as a beat
addition and cancellation) as a single tone at about the average of
the two frequencies and an AM modulation at the difference of the two
frequencies. Obviously, if the beat is very long period, you have to
hear the two beating tomes for a cycle or two of the beat period to
detect that effect. Harmonically related tones just produce a
repeating pattern at some integer multiples of each of the component
frequencies. This can produce a very pleasing effect. You hear sound
from one musical source as a fundamental and several harmonically
related frequencies. If a second musical source (a harmonizing voice,
for example) has its fundamental at one of the harmonics of the other
signal, your brain recognizes this simple multiple relationship as a
pleasing musical harmony. For some ratios. This page shows some of
the approximate ratios between notes that sound interesting together:
http://www.jimloy.com/physics/scale.htm

When they talk about harmonics in an electrical wave, I guess they're
talking about the potential for energy transfer.

Not really. since linear circuit components react to many frequencies
by the addition if the effect of each frequency, it is a very powerful
analytical procedure to break a signal down into its harmonics and
evaluate the response of a circuit to each of those harmonics, and add
all the effects together to get the total response.

In that case, only odd
multiples of the fundamental will stay in phase to tap the energy from
the distortion.

Symmetrical distortion of a sine wave (shape of positive half cycle is
a mirror image of that on the negative half cycle) can be shown to be
made up of only the fundamental and odd harmonics (3 times. 5 times,
etc.). If the distortion peaks up one half cycle and flattens the
other or shifts the zero crossing so that one half cycle lasts longer
than the other, there are even harmonics in the wave shape. There may
also be odd ones, too. Got to do that Fourier analysis to quantify that.

Where a wave is flattened it may resemble part of a
sine curve with a longer period than the fundamental, but that doesn't
count because you can't tap energy from the flat part.

You can with a resistor. From a Fourier perspective, that flat part
just represents a time when the curve of some frequencies is nearly
canceled by the curve from other frequencies. You need an infinite
number of harmonics to make a truly flat square wave with perfectly
square corners.

If there's any truth in what I've said, I'll forget in a flash. In 1975
I was working in a repair facility. We'd use Bird Wattmeters to see
forward and reflected power in antenna feeds. We knew the jargon and
how to use the meters, but one day it struck me that none of us
understood why they worked. I had a flash of insight and everybody
stopped work to listen to me explain. Their faces lit up with
comprehension. I felt pretty smart. The next day I couldn't remember
whatever it was I'd figured out.

I hate it when that happens.

On Mon, 13 Jun 2005 11:59:48 -0800, (Floyd L.
Davidson) wrote:

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

Reality check! Capacitors are passive devices. They do *NOT*
generate signals.

---
Hah! Just as I thought you would, you disingenuous little ****, you
snipped my:

"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'."

for the purpose of being able to reiterate the obvious. Seems that's
one of your devices, reiteration. Jumble the right with the wrong,
but just keep saying them over and over and perhaps you'll confuse
someone with a lower mentality than yours into believing that you know
what you're talking about. Not bloody likely, boyo, since someone
like that would be hard to find outside of Mickey D's and you're about
as transparent as they come.

BTW, capacitors, (even though passive) are quite capable of actually
generating signals. Consider ceramic capacitors with lead
zirconate-titanate dielectrics. Often capable of _generating_
acoustic signals. Also consider passive electrets. Nice little
microphones they are. And, even parametrically varying caps can be
used as pumps to _generate_ RF signals.

But, I digress... We're really talking about your colors starting to
show and what a dishonest little sneak you're turning into.
---

All that has happened is the capacitor does not pass DC. You
haven't generated AC on one side, you've merely removed the DC.

I don't see how that could be any more obvious. You did take
a high school physics class, didn't you? *Use* what you learned!

---
Rather than merely parroting: "removing the DC", ad nauseam, it might
be helpful if you actually studied the mechanism which causes that
phenomenon to occur. Hint: the capacitor allows the load to "float"
without regard to the voltage on the other side of the cap since
there's a galvanic barrier between the load and its driver.
---

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.

Okay, so you not only need to restudy high school physics, but
differential equations too.

---
No, for this exercise all I have to do is point out the untenability
of your position and watch you squirm trying to work your way out from
under my thumb.
---

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.

If you had read the definition you posted, you might have
noticed that it perfectly described the remark that I was
commenting on. It had nothing to do with the discussion.

---
If you think that what I posted was a non sequitur, then I invite you
to expound on why you think that.
---

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

You are the one stooping to spelling flames.

---
A correction isn't a flame unless you take it that way.

--
John Fields
Professional Circuit Designer

On Mon, 13 Jun 2005 12:10:18 -0800, (Floyd L.
Davidson) wrote:

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

Oh, my. And you said what about Emily Post.

---
I said nothing about Emily Post. What I alluded to was that you have
bad manners and could use a little training in etiquette.
---

Nothing I said was a flame. And I'd suggest you go practice (a *lot*)
before you try me on for a flame war. Especially if you think *that*
is a flame.

---
Oh, my! She says one thing, then does another and pulls herself up to
her full 4 foot height and threatens to strike a match! Don't forget
what your mommy taught you about playing with fire.
---

I'm starting to think you're having a real problem with reading
comprehension.

Apparently I read a lot better than you write.

---
More unsubstantiated twaddle.
---

I write that for the current in a load to alternate,

You write a lot of things that are not valid.

---
Just because you can't understand them doesn't mean they're not valid.
---

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

Do you understand that is not significant?

---
It most certainly _is_, since it's what determines the difference
between fluctuating direct current and true alternating current.
---

The reactance of circuit
components, the fundamental significance of AC circuit analysis, does
not depend upon polarity alternation in any way. What else is there
to talk about? How many chocolate drops should be in each chocolate
chip cookie? I await your essay on *something* of significance.

---
Well, since you consider matters of significance to be what you can
understand and what pleases your ego, it's not likely that your wait
will bear fruit.
---

But please, that is the *end* of discussion on your confusion about
AC.

---
I see. You've come to the end of your rope and your exit strategy is
to make it seem like everyone is wrong but you.

--
John Fields
Professional Circuit Designer

John Fields wrote:
Hah! Just as I thought you would, you disingenuous little ****, you
snipped my:
....
what you're talking about. Not bloody likely, boyo, since someone
like that would be hard to find outside of Mickey D's and you're about
as transparent as they come.
....
But, I digress... We're really talking about your colors starting to
show and what a dishonest little sneak you're turning into.
....
No, for this exercise all I have to do is point out the untenability
of your position and watch you squirm trying to work your way out from
under my thumb.
....
A correction isn't a flame unless you take it that way.

Your flaming is as poor as your electrical theory.

You need to get a handle on your temper as well as learn some
manners and some theory.

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

On Mon, 13 Jun 2005 15:38:18 -0800, (Floyd L.
Davidson) wrote:

John Fields wrote:
Hah! Just as I thought you would, you disingenuous little ****, you
snipped my:
...
what you're talking about. Not bloody likely, boyo, since someone
like that would be hard to find outside of Mickey D's and you're about
as transparent as they come.
...
But, I digress... We're really talking about your colors starting to
show and what a dishonest little sneak you're turning into.
...
No, for this exercise all I have to do is point out the untenability
of your position and watch you squirm trying to work your way out from
under my thumb.
...
A correction isn't a flame unless you take it that way.

Your flaming is as poor as your electrical theory.

You need to get a handle on your temper as well as learn some
manners and some theory.

---
Hmmm....
Seems like I've picked up a secretary/archivist.
Categorize and file away, honey!

Yawnnnn...

--
John Fields
Professional Circuit Designer

John Fields wrote:
I said nothing about Emily Post. ...
....
Oh, my! She says one thing, ...
....
More unsubstantiated twaddle.
....
Just because you can't ...
....
---
It most certainly _is_, since it's what determines the difference
between fluctuating direct current and true alternating current.
---
....
Well, since you consider matters of significance ...
....
I see. You've come to the end of your rope ...

One statement (quoted in full above) that (even though wrong) at
least has something to do with the topic, Six out of seven
comments are piddly attempts a childish and gratuitous insults.

No discussion John. I don't waste time teaching basics to grown
men who have temper tantrums in public.

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