Making sense of watts, amps and volts -- a typo?

[John G]

W. eWatson wrote :

Could the following be a typo. Written by someone to me on inverters (DC to
AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up to
maintain the same number of watts.

1000 watts at 120VAC is about 8.3 amps.
1000 watts at12VDC is about 83 amps. <--typo? Shouldn't it still be 8.3?

As usual this simple question developed into a slanging match between 2
or 3 smart a**es who seem to have more time to type than think.

They cannot argue a year or more's Engineering study in a series of one
line snipes.

So come on you arguing children please try and keep to the question
and not display what pedantic idiots you appear to be.

All that stuff about AC is undoubtably true but had little to do with
the guts of the question and would only confuse some one who asked a
very simple question which deserved a simple answer.

--
John G

 

[krw@att.bizzzzzzzzzzzz]

On Sun, 08 Apr 2012 23:29:20 GMT, Chiron
<chiron613.no.spam.@no.spam.please.gmail.com> wrote:

On Sun, 08 Apr 2012 17:23:25 -0400, krw@att.bizzzzzzzzzzzz wrote:

I'm largely self-taught.

It shows.

There is nothing to be ashamed of in being self-taught. Lots of highly
competent people learned their skills on their own, without teachers.

I agree, as long as you did a good job. I've worked with some excellent
self-taught engineers. JF and "Jamie" clearly don't qualify as more than
hacks.

Considering the quality of college graduates, at least in the US, having
a degree isn't particularly impressive. The quality of EE's is better,
true, but it's still no guarantee of competence.

Again, I agree. It's how I got my job, even as a white hair. The boss
doesn't trust recent graduates (recent ~= 20-30 years). ;-)

 

[krw@att.bizzzzzzzzzzzz]

On Sun, 08 Apr 2012 17:36:22 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Sun, 08 Apr 2012 16:48:21 -0400, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:

On Sun, 08 Apr 2012 14:43:57 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sun, 08 Apr 2012 11:57:56 -0400, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:

On Sun, 08 Apr 2012 10:18:16 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sun, 08 Apr 2012 09:53:38 -0400, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:

On Sun, 08 Apr 2012 03:59:19 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sat, 07 Apr 2012 20:18:26 -0400, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:


On Sat, 07 Apr 2012 17:02:40 -0700, "W. eWatson" <wolftracks@invalid.com
wrote:

Could the following be a typo. Written by someone to me on inverters (DC
to AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up
to maintain the same number of watts.

This isn't strictly true for AC.

---
P
How does I = --- manage to not work out for AC?
E

PF, dumbass.

---
Watts is watts...

But, as any first-year engineering student knows, I * V <> W, where AC is
concerned.

---
If you had perspicacity, and could read between the lines, you'd have
noticed that the OP couched his query in terms of watts, implying the
load was resistive.

Moron, reading between the lines, anyone with as much as half a brain, would
understand that he was talking about an INVERTER, which is *NOT* resistive.

---
Really?

Really.

With PFC on the input and a resistive load on the output it would look
just like a resistor connected across the mains.

SHows how much you know about garden variety inverters.

---

But, since you don't, you missed that the cosine of the phase angle
between voltage and current - in the resistive load he alluded to -
would be 1, and volt-amperes would be precisely equal to watts.

What a dumbass.

---
Epithets instead of reasoned dialogue?

The facts speak for themselves.

What a surprise...

That I call a spade a spade? No, it really isn't. You're nothing but a
pompous hack.

---

And, by the way, any first-year engineering student would have been
taught that, in a reactive circuit, your: "I * V <> W" is nonsense
since volt-amperes can be greater than - but never less than - watts.

What a stupid twit. "<>" == NOT EQUAL TO

---
Yes, of course, but you dodge, since your "I * V <> W" fails when the
load is resistive and I * V = W.

A fact not in evidence.

You also seem to have missed the point that, when the load is
reactive, I * V will always be greater than W.

What a dumbass. ">" is satisfied by "<>".

---

I guess you never made it that far, though...

Like I said, you're as dumb as AlwaysWrong. Keep proving it.

---
What you've said doesn't prove that you're right, it only proves that
you prefer invective over reason.

Absolutely wrong. You continue to prove that you're nothing but a hack. An
illiterate one, at that.

---

Go back to your 555s.

---
Interesting that those of you who haven't been able to get a handle on
how to use a 555 efficaciously, for any purpose, try to use your
ignorance to make us, who use them with delight, seem inferior.

Like AlwaysWrong, you insist on proving that you're *always* wrong.

---
More abject nonsense.

The total truth.

I've been here for about 15 years and have provided solutions for
problems which you rail against because of your ineptitude.

LOL! What a loser.

---

I have
nothing against the 555, just one-trick-ponies, like you.

---
Geez, I guess you haven't perused my posting history.

555 after 555. Silly pedantic argument after silly pedantic argument.
What a moron.

---


You're as dumb as DimBulb.

---
Perhaps, but it seems you still have a long way to go before you get
here.

AlwaysWrong.

---
Indeed.

At least you now accept the truth, AlmostAlwaysWrong.

 

[krw@att.bizzzzzzzzzzzz]

On Sun, 08 Apr 2012 23:38:27 GMT, Chiron
<chiron613.no.spam.@no.spam.please.gmail.com> wrote:

On Sun, 08 Apr 2012 15:47:42 -0500, John Fields wrote:

There's no such thing as "RMS power." ---

As I try to follow along through this thread, I find myself having to
wade through more and more bullshit just to get to some facts - and even
then, I am never clear whether the fact is accurate.

Power is power. RMS voltage and RMS current have meaning because you square
them (V or I) to calculate power. The RMS is the "effective" voltage or
current, when talking about power/energy. What does squaring power get?
*AVERAGE* power (sometimes over a fixed time) is the meaningful quantity.

I don't see why there couldn't be something called RMS power, though I've
never heard of such a thing. A cite would be very helpful.

What is the meaning of power squared?

The continued exchange of insults, while amusing, doesn't do much to help
someone learn.

True. Some here have to pick pedantic fights. It's all they do.

 

[krw@att.bizzzzzzzzzzzz]

On Mon, 09 Apr 2012 09:55:37 +1000, John G <greentest@ozemail.com.au> wrote:

W. eWatson wrote :
Could the following be a typo. Written by someone to me on inverters (DC to
AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up to
maintain the same number of watts.

1000 watts at 120VAC is about 8.3 amps.
1000 watts at12VDC is about 83 amps. <--typo? Shouldn't it still be 8.3?

As usual this simple question developed into a slanging match between 2
or 3 smart a**es who seem to have more time to type than think.

They cannot argue a year or more's Engineering study in a series of one
line snipes.

So come on you arguing children please try and keep to the question
and not display what pedantic idiots you appear to be.

All that stuff about AC is undoubtably true but had little to do with
the guts of the question and would only confuse some one who asked a
very simple question which deserved a simple answer.

Which he got.

 

[John G]

krw@att.bizzzzzzzzzzzz formulated on Monday :

On Mon, 09 Apr 2012 09:55:37 +1000, John G <greentest@ozemail.com.au> wrote:

W. eWatson wrote :
Could the following be a typo. Written by someone to me on inverters (DC to
AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up to
maintain the same number of watts.

1000 watts at 120VAC is about 8.3 amps.
1000 watts at12VDC is about 83 amps. <--typo? Shouldn't it still be
8.3?

As usual this simple question developed into a slanging match between 2
or 3 smart a**es who seem to have more time to type than think.

They cannot argue a year or more's Engineering study in a series of one
line snipes.

So come on you arguing children please try and keep to the question
and not display what pedantic idiots you appear to be.

All that stuff about AC is undoubtably true but had little to do with
the guts of the question and would only confuse some one who asked a
very simple question which deserved a simple answer.

Which he got.

Along with a lot of confusing arguments and insults from you and a
couple of others. :-[

--
John G

 

[Chiron]

On Sun, 08 Apr 2012 20:24:27 -0400, krw@att.bizzzzzzzzzzzz wrote:

What is the meaning of power squared?

What is the meaning of voltage squared?

I'm not trying to claim that there *is* any such thing as RMS power; just
wondering why such a thing would be impossible.

The only thing I can figure is that power never becomes negative - it
fluctuates, can drop to zero, but not below. So maybe RMS wouldn't apply
to that; but I honestly can't see why it couldn't.

It's a shame that the thread got so contentious. I'm sure I could learn
things, except for the bickering... Oh, well. I've participated in
enough flame wars in my time to not be too critical.

--
nolo contendere:
A legal term meaning: "I didn't do it, judge, and I'll never do
it again."

 

[krw@att.bizzzzzzzzzzzz]

On Mon, 09 Apr 2012 10:50:43 +1000, John G <greentest@ozemail.com.au> wrote:

krw@att.bizzzzzzzzzzzz formulated on Monday :
On Mon, 09 Apr 2012 09:55:37 +1000, John G <greentest@ozemail.com.au> wrote:

W. eWatson wrote :
Could the following be a typo. Written by someone to me on inverters (DC to
AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up to
maintain the same number of watts.

1000 watts at 120VAC is about 8.3 amps.
1000 watts at12VDC is about 83 amps. <--typo? Shouldn't it still be
8.3?

As usual this simple question developed into a slanging match between 2
or 3 smart a**es who seem to have more time to type than think.

They cannot argue a year or more's Engineering study in a series of one
line snipes.

So come on you arguing children please try and keep to the question
and not display what pedantic idiots you appear to be.

All that stuff about AC is undoubtably true but had little to do with
the guts of the question and would only confuse some one who asked a
very simple question which deserved a simple answer.

Which he got.

Along with a lot of confusing arguments and insults from you and a
couple of others. :-[

I answered correctly. Fields then had one of his patented hissy fits pulling
the discussion off topic. Can't do anything about him.

 

[krw@att.bizzzzzzzzzzzz]

On Mon, 09 Apr 2012 00:57:45 GMT, Chiron
<chiron613.no.spam.@no.spam.please.gmail.com> wrote:

On Sun, 08 Apr 2012 20:24:27 -0400, krw@att.bizzzzzzzzzzzz wrote:

What is the meaning of power squared?

What is the meaning of voltage squared?

Power (P=V^2/R).

I'm not trying to claim that there *is* any such thing as RMS power; just
wondering why such a thing would be impossible.

Not impossible, just meaningless.

The only thing I can figure is that power never becomes negative - it
fluctuates, can drop to zero, but not below. So maybe RMS wouldn't apply
to that; but I honestly can't see why it couldn't.

Does voltage squared ever go negative? ;-)

It's a shame that the thread got so contentious. I'm sure I could learn
things, except for the bickering... Oh, well. I've participated in
enough flame wars in my time to not be too critical.

Read the direct responses to your questions and ignore the ankle biters, like
Fields. He's only trying to prove his dick is bigger than it is; a
professional pedant.

 

[amdx]

LOL! What a loser.

---

I have
nothing against the 555, just one-trick-ponies, like you.

---
Geez, I guess you haven't perused my posting history.

555 after 555. Silly pedantic argument after silly pedantic argument.
What a moron.
---


You're as dumb as DimBulb.

---
Perhaps, but it seems you still have a long way to go before you get
here.

AlwaysWrong.

---
Indeed.

At least you now accept the truth, AlmostAlwaysWrong.

What's up, KRW?
You seem unusually contentious this evening.
It's unusual.

This whole thread got out of hand pretty quickly for
a subject that could have been handled with one sentence.
Then a couple more if phase angle needed to be addressed.
Mikek

 

[Jasen Betts]

On 2012-04-08, Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

John Fields wrote:


---
There's no such thing as "RMS power."
---

Oh really..

There is as RMS can be taken for any time vaying quantity,
but I don't think it's what you think it is.

RMS means square-Root, of the Mean, of the Square

eg: put 1V at 1kHz into an ideal capacitor of the right size,

V=√2sin(2000πt+ϕ) "sqrt(2) sin( 2000 pi t + phi )"
I=√2cos(2000πt+ϕ)

to compute the instantaneous power multiply those,
you'll eventually get

P=sin(4000πt+2ϕ)

SQUARE that, it'll come out to

0.5+0.5sin(8000πt+4ϕ)

and take the MEAM

0.5

and then the square ROOT

1/√2 "1/sqrt(2)"

Which must mean something, but doesn't appear to be useful to me.
certainly it is neither the mean power (0W) nor the reactive
power (1VA)

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[Chiron]

On Sun, 08 Apr 2012 21:09:52 -0400, krw@att.bizzzzzzzzzzzz wrote:

Does voltage squared ever go negative? ;-)

No, but the voltage can.



--
It's a lot of fun being alive ... I wonder if my bed is made?!?

 

[John Larkin]

On Mon, 09 Apr 2012 09:55:37 +1000, John G <greentest@ozemail.com.au>
wrote:

W. eWatson wrote :
Could the following be a typo. Written by someone to me on inverters (DC to
AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up to
maintain the same number of watts.

1000 watts at 120VAC is about 8.3 amps.
1000 watts at12VDC is about 83 amps. <--typo? Shouldn't it still be 8.3?

As usual this simple question developed into a slanging match between 2
or 3 smart a**es who seem to have more time to type than think.

They cannot argue a year or more's Engineering study in a series of one
line snipes.

So come on you arguing children please try and keep to the question
and not display what pedantic idiots you appear to be.

The question is not clearly stated.

John

--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Jamie]

krw@att.bizzzzzzzzzzzz wrote:

On Sun, 08 Apr 2012 23:29:20 GMT, Chiron
chiron613.no.spam.@no.spam.please.gmail.com> wrote:


On Sun, 08 Apr 2012 17:23:25 -0400, krw@att.bizzzzzzzzzzzz wrote:


I'm largely self-taught.

It shows.

There is nothing to be ashamed of in being self-taught. Lots of highly
competent people learned their skills on their own, without teachers.


I agree, as long as you did a good job. I've worked with some excellent
self-taught engineers. JF and "Jamie" clearly don't qualify as more than
hacks.

Still on the meds I see?

Putting all your bull shit aside, I don't see you as much of a prize
winner, unless you want to count on how much of ass you really are. And
take my word for it, you are an ass. I doubt very much there are many
here that would say otherwise in your behalf.

As far as JF being a hack? I've seen more material come out of him
that would actually work with plenty of help behind it to support those
that are interested. You on the other hand would rather sit there in
your natural domain and make an ass out of yourself. And you do that
very well. Must be one of your strong points.

Maybe JF hasn't had technical schooling in this subject, as "I" and
many others here, have however, I can say that his offerings are much
more interesting to look at rather than your material, which is most of
nothing.

As for myself, You may perceive me as a hack, most likely because you
yourself just assume it is safer that way. You know, just follow the
sheep. Well, you are one of the sheep. I doubt if you could even
truly be able to identify who is and what constitutes a hack/hacker.

I may not get along with every one here on a social level and there
are a few that come in now and then with bad attitudes, some of those
actually know a lot more that you and I am beginning to understand their
reason for being that way.

I've been doing this for 45 years, enrolled in many update courses
over the years, sat in on many interviews for EE positions, why?
because they trust my opinion. Must be a reason for it, do you think ?


Yes, a fine piece of work you are. If you only knew what you really
look like here.

I've seen a lot of bull shit over the years and I've seen many that
would appear to the academic world as being incapable, inadequate, not
qualified, does not know any, but, they can blow circles around those
passing judgment like that and leave them in the smoke with nothing but
a grin on their face as they look back. I am sorry to say, you aren't
one of those, Your just one of the sheep.

As much as I may disagree with JF's way of conducting business in his
attempt to get back at people. He does not deserve what he gets for his
help to those that are seeking help. When you become part of the gang
bang with out knowing who and what you're doing it for, you are then
just a sheep and worthless. Maybe you should step out of the herd and
see things for the way they really are.

Jamie

 

[Chiron]

On Sat, 07 Apr 2012 17:02:40 -0700, W. eWatson wrote:

Could the following be a typo. Written by someone to me on inverters (DC
to AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up
to maintain the same number of watts.

1000 watts at 120VAC is about 8.3 amps. 1000 watts at12VDC is about 83
amps. <--typo? Shouldn't it still be 8.3?

Look, the OP long ago admitted that he had mis-read the text, which led
to his confusion. It was a simple enough mistake that any one of us
could have made - and that all of us probably have at one time or another.

To see this simple issue degenerate into bitter name-calling and insults
is sad. I can kind of understand this in politics, or things like
psychology, religion, etc., where there is no objective way to arrive at
a conclusion. It makes very little sense for it to happen when it is
easy enough to post a relevant equation or perhaps a link to convincing
sources, something like that.

I can pretty much guarantee that I'm going to slip up and say something
dumb one of these days. Maybe I'll have forgotten something, or applied
the wrong equation, or simply made a typo. I can do all of these things
without having to be a complete idiot. In fact, there is no one who
*doesn't* make mistakes and say dumb things; it doesn't make them stupid.

If people here jump all over me and insult me, it's not going to trouble
me much. I already know I'm not stupid; and I already know I'm not
perfect. Call me an idiot, I'll know you're wrong. Tell me I'm wrong,
and especially show me *where* I'm wrong, and I'll admit my mistake. No
biggie.

But you've got guys here who *are* new, who really don't know how things
work yet, and are trying to learn. If they see people getting jumped on,
they may decide to try to learn somewhere else. That's a shame, because
it seems that there are people here who *do* know what they're talking
about, who have something to offer.

Even sadder, there really aren't all that many people out there who give
a shit about electronics in the first place. I live in Chicago, where
there are shitloads of people, and I rarely ever encounter anyone who
cares about electronics beyond wanting to get an iPod. That makes it
kind of lonely when you want to talk about this stuff. Mention
electronics, and people start to edge away from you like you were trying
to convert them or something.

So it saddens me to see this bickering, because I suspect there are folks
out there who are scared away from here, afraid to ask a question lest
everyone assure them they're utterly stupid.

OK, enough of my little soapbox. Insults to /dev/null, and insulters to
the killfile. Respectful criticisms respectfully answered.

--
I'm a fuschia bowling ball somewhere in Brittany

 

[Jasen Betts]

On 2012-04-09, Chiron <chiron613.no.spam> wrote:

On Sun, 08 Apr 2012 20:24:27 -0400, krw@att.bizzzzzzzzzzzz wrote:

What is the meaning of power squared?

What is the meaning of voltage squared?

it's proportional to power in a resistor,
(divide it by resistance to get power)

I'm not trying to claim that there *is* any such thing as RMS power; just
wondering why such a thing would be impossible.

it's can be measured and computed, but I'm not sure what it's good for.

The only thing I can figure is that power never becomes negative

It can, eg: when a battery is being charged the battery has a negative
power output,

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[Bob Myers]

On Sunday, April 8, 2012 6:57:45 PM UTC-6, Chiron wrote:

On Sun, 08 Apr 2012 20:24:27 -0400, krw@att.bizzzzzzzzzzzz wrote:

What is the meaning of power squared?

What is the meaning of voltage squared?

I'm not trying to claim that there *is* any such thing as RMS power; just
wondering why such a thing would be impossible.

Obviously it's not - "RMS" (root-mean-square) is simply a
mathematical means for getting a meaningful "average" value,
particularly for cases where the actual "average" would be
zero (as in the case of a zero-offset sinusoid). You can most
certainly square any function, average it over a suitable period,
and then take the square root of that mean value, which would
be the "RMS" value of that function. The only remaining question
is whether or not it's useful to do so in any given case.

So you could certainly calculate an "RMS" value for power, or
for voltage, or for the Dow Jones average over the past year
if you like.

But to get back to the original question - I've also heard the
term "RMS power" intended (rather sloppily, but it was at least
understood) to mean "true power." Not exactly the best use of
that term, but generally no one gets too bent out of shape about
it other than the sorts of pedants we see exemplified in this
thread.

Bob M.

The only thing I can figure is that power never becomes negative - it
fluctuates, can drop to zero, but not below. So maybe RMS wouldn't apply
to that; but I honestly can't see why it couldn't.

It's a shame that the thread got so contentious. I'm sure I could learn
things, except for the bickering... Oh, well. I've participated in
enough flame wars in my time to not be too critical.

--
nolo contendere:
A legal term meaning: "I didn't do it, judge, and I'll never do
it again."

 

[Chiron]

On Sun, 08 Apr 2012 21:24:29 -0700, Bob Myers wrote:

On Sunday, April 8, 2012 6:57:45 PM UTC-6, Chiron wrote:
On Sun, 08 Apr 2012 20:24:27 -0400, krw@att.bizzzzzzzzzzzz wrote:

What is the meaning of power squared?

What is the meaning of voltage squared?

I'm not trying to claim that there *is* any such thing as RMS power;
just wondering why such a thing would be impossible.

Obviously it's not - "RMS" (root-mean-square) is simply a mathematical
means for getting a meaningful "average" value, particularly for cases
where the actual "average" would be zero (as in the case of a
zero-offset sinusoid). You can most certainly square any function,
average it over a suitable period, and then take the square root of that
mean value, which would be the "RMS" value of that function. The only
remaining question is whether or not it's useful to do so in any given
case.

So you could certainly calculate an "RMS" value for power, or for
voltage, or for the Dow Jones average over the past year if you like.

But to get back to the original question - I've also heard the term "RMS
power" intended (rather sloppily, but it was at least understood) to
mean "true power." Not exactly the best use of that term, but generally
no one gets too bent out of shape about it other than the sorts of
pedants we see exemplified in this thread.

Bob M.

Actually, that was what my vague wonderings were trying to get at. I
remembered that RMS had *something* to do with values going negative; but
I couldn't remember the details. Of course, what I was groping for only
applied to the values that tended to average out to zero, so I was still
pretty wide of the mark... Oh, well.

It's kind of strange to find pedantry in an electronics group. Back in
the day (late seventies, early eighties) we were happy if we were within
10% of reality.


--
Yow! Are we laid back yet?

 

[John Fields]

On Sun, 08 Apr 2012 14:10:19 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sun, 08 Apr 2012 15:53:20 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sun, 08 Apr 2012 13:40:56 -0700, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sun, 08 Apr 2012 14:43:57 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sun, 08 Apr 2012 11:57:56 -0400, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:

On Sun, 08 Apr 2012 10:18:16 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sun, 08 Apr 2012 09:53:38 -0400, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:

On Sun, 08 Apr 2012 03:59:19 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sat, 07 Apr 2012 20:18:26 -0400, "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote:


On Sat, 07 Apr 2012 17:02:40 -0700, "W. eWatson" <wolftracks@invalid.com
wrote:

Could the following be a typo. Written by someone to me on inverters (DC
to AC).


Volts x Amps = Watts so as the voltage goes down, the amperage goes up
to maintain the same number of watts.

This isn't strictly true for AC.

---
P
How does I = --- manage to not work out for AC?
E

PF, dumbass.

---
Watts is watts...

But, as any first-year engineering student knows, I * V <> W, where AC is
concerned.

---
If you had perspicacity, and could read between the lines, you'd have
noticed that the OP couched his query in terms of watts, implying the
load was resistive.

But, since you don't, you missed that the cosine of the phase angle
between voltage and current - in the resistive load he alluded to -
would be 1, and volt-amperes would be precisely equal to watts.

And, by the way, any first-year engineering student would have been
taught that, in a reactive circuit, your: "I * V <> W" is nonsense
since volt-amperes can be greater than - but never less than - watts.

I guess you never made it that far, though...


What engineering school did you graduate from?

---
None.

I'm largely self-taught.

Then your comments about what first-year engineering students would
have been taught, and people not making it that far, are absurd.

---
In your intense desire to insult, you seem to have glossed over the
fact that it was krw - not I - who claimed that the effects of
reactance were taught to first-year engineering students.

I merely followed his lead, assuming that he was familiar with
first-year engineering course work, so your insult was clearly
misdirected.
---

I don't recall learning about reactive power first-year; that was more
like year 2 or 3, when I took the electric machinery courses.

---
Well, now I'm in a quandary in that you and krw seem to have different
opinions on what is taught when, so I don't know who to believe.

Why don't you two miscreants work it out between yourselves?

--
JF

 

[John Fields]

On Sun, 08 Apr 2012 14:13:14 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sun, 08 Apr 2012 15:47:42 -0500, John Fields
jfields@austininstruments.com> wrote:

On Sun, 08 Apr 2012 16:03:02 -0400, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

John Fields wrote:

On Sun, 08 Apr 2012 09:39:37 -0700, Fred Abse
excretatauris@invalid.invalid> wrote:


On Sun, 08 Apr 2012 10:18:16 -0500, John Fields wrote:


Watts is watts...

But ain't always Volt-Amperes.


---
Of course, but since the OP couched his problem in terms of watts,
then VA is irrelevant.


When I see the term "VA", I know we're dealing with "REACTIVE" power.

PF (Power Factors) denotes the difference between "REACTIVE" and
"RESISTIVE (True power)" So, using the term VA is assumed power.

Having AC in the equation has nothing to do with it actually, I can
put AC into a purely non reactive load and it would simply power.. There
difference being is, you need to take measurements along the vectors to
come with a sum of power with in a time frame. Normally, with a clean
sinusoidal wave, we just assume RMS power.

---
There's no such thing as "RMS power."


The term is commonly used to mean "true power", as measured by a "true
RMS" instrument.

---
Dance around all you like, the term is still wrong.

--
JF