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

[Jamie]

No, when you se "VA" you simply don't know "W"; not enough information given.
With an inverter you can *bet* the power factor is not unity.




What? Did you really mean to write that nonsense?




You've just specified the PF by stating a resistive load, so no, you're still
wrong. Without the PF explicitly stated you *cannot* get there from here.




Your "COS(X)" *is* the power factor, which is only true for sine waves.




WTF, is the COS(X) term, if not to cover reactive power? Jamie, go back to
your ham shack.

How lonely you must be.

Isn't it a bitch when sitting there late at night scratching your
balls because you, just don't get what you though you did.

Sorry, But you failed, again.

As for Ham radio, that is just a Hobby and social hour get-together, I
actually do work in the Electrical/Electronics field and I do very well
at it. I take that opinion from bonuses, raises and royalties earned.
I've never had a problem being employed and been so for many years
performing engineering level work. I guess If "I" was so miss led as you
seem to think, our company that I work for would have been in trouble
years ago.

Oh btw, I used to work for a company that made electronic components
for the patriot missiles. Yes, the actual electronics involved in the
missiles and transport. I bet that really scares you now !

I must say, ignorance is bliss.

Put the beer down, it's impairing your judgment.

Jamie

 

[Jasen Betts]

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(4000Ï€t+2Ï•)

SQUARE that, it'll come out to

0.5+0.5sin(8000Ï€t+4Ï•)

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)

 

[Chiron]

I first encountered it in college in calc class and then in second
semester physics. ...both first year.

I got it in the first year - electronics engineering technology, not a
real EE. I guess it really doesn't make a whole lot of difference when
it's taught, as long as the students have learned the basic math -
complex numbers, phasors, some trig, the various tricks like ... hmm...
whatever it was called (30 years ago; I forget). DeMoivre's theorem,
maybe?

These are all pretty fundamental concepts that don't require much
preparation except for some math.

 

[Chiron]

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.

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.

 

[Chiron]

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.

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.

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

 

[[email protected]]

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). ;-)

 

[[email protected]]

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.

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.

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.

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

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.

555 after 555. Silly pedantic argument after silly pedantic argument.
What a moron.
At least you now accept the truth, AlmostAlwaysWrong.

 

[[email protected]]

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.

 

[[email protected]]

W. eWatson wrote :

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.

 

[Chiron]

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.

 

[[email protected]]

[email protected] formulated on Monday :

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.

 

[[email protected]]

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.


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

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

 

[Chiron]

Does voltage squared ever go negative? ;-)

No, but the voltage can.

 

[Jamie]

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]

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.

 

[Jasen Betts]

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,

 

[Chiron]

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.

 

[Jamie]

---
Yes, really.
---




---
Now that you've been shown the trick it's easy to back-pedal and claim
you knew it all along but "slipped" on the keyboard.

I'd be naive if I believed it _was_ a slip.
---




---
"Punching at the bit?"

What's that supposed to mean?
---




---
How so?

I pointed out both of your errors and fixed one, so I certainly have a
better understanding than you do of what you pretend to know.
---




---
You just can't seem to open your mouth without sticking your foot in
there, can you?
---




---
Again, there is no such thing as RMS power.
---




---
As far as help is concerned, the most you could do would be to learn
to shut the **** up.

failing that, at least try to learn how to construct a sentence
properly.

You're starting to take on the traits of Phil A.
Now it's only a toss up as to who knows more.

Please be more realistic..

And btw, Your still in the dark about this.

Jamie

 

[Chiron]

You seem to have been taught that you can catch more flies with vinegar
than with honey.

You seem to have been taught that there is some benefit to catching flies.