See http://en.wikipedia.org/wiki/Mains_electricity and http://www.tpi-thevalueleader.com/rms.html
AC voltage goes from 0 to its peak (120 or 240) and back to 0 (in US, 60 times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).
So what's the real voltage? Not 120, since it's only there an instant. Not 0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.
Your meter can't keep up with changes, so it reads a happy number somewhere in between also.
Many inverters (DC to AC converters) and many types of power supplies, simply chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.
Other applications may have a saw tooth shape.
They both have enough of what's underneath the camel's hump to work.
Your homework assignment for tomorrow is to tell the group what I just said in a way that makes sense.
:)
Looking at the camel's hump, you can see it isn't a simple average since there's less area under the peak than points under the rest of the graph.
Tex wrote:
...
> The only question I'd raise is whether all camel humps follow simple
> sine waves or whether some vary and follow the curve of more complex
> trig functions. I suspect the latter. However, not having a herd of
> camels conveniently nearby I'll have to leave that question to others
> who, perhaps, do.
...
Mr Fourier showed it's possible to make up all the various trig
functions as a combination of camels of varying ages and walking at
various relative speed... :)
[email protected] wrote:
> See http://en.wikipedia.org/wiki/Mains_electricity and http://www.tpi-thevalueleader.com/rms.html
>
> AC voltage goes from 0 to its peak (120 or 240) and back to 0 (in US, 60 times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).
>
> So what's the real voltage? Not 120, since it's only there an instant. Not 0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.
>
> Your meter can't keep up with changes, so it reads a happy number somewhere in between also.
>
> Many inverters (DC to AC converters) and many types of power supplies, simply chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.
>
> Other applications may have a saw tooth shape.
>
> They both have enough of what's underneath the camel's hump to work.
>
> Your homework assignment for tomorrow is to tell the group what I just said in a way that makes sense.
>
> :)
>
> Looking at the camel's hump, you can see it isn't a simple average since there's less area under the peak than points under the rest of the graph.
For energy transfer, you're looking at the time average of voltage x
current, which for a
linear (non-switching) load works out to root-mean-square voltage x
root-mean-square current x power-factor (cos of phase-angle)
Square root of average of square of waveform is the key. For sinusoid,
works out to 2^.5
times peak voltage/current. Other waveforms are susceptible to .same
calculus.
No biggie.
J
Tex wrote:
> The only question I'd raise is whether all camel humps follow simple
> sine waves or whether some vary and follow the curve of more complex
> trig functions. I suspect the latter.
Very simple sine waves.
It's not a question of it being difficult to make a pure sine wave,
it's the question of it starting as a fundamentally pure sine wave and
any extra distortion needing to be added to it as higher frequency
components. This is energy and it has to come from somewhere.
Of course there will be some distortion, because some extra waves do
find their way in -- but the waveform of long-distance power
transmission is pretty clean. Those long powerlines are quite a
low-pass good filter of medium frequencies. If you do get noise, it
tends to be sharp spikes (switching spikes, lightning) and these are
acquired locally.
[...snip...]
they both have enough of what's underneath the camel's hump to work.
>
>Your homework assignment for tomorrow is to tell the group what I just said in a way that makes sense.
>
>:)
>
Hmm, you want a lecture on calculus?
Take the sine wave and square wave curves, plot them on a piece of
paper, cut them out, weigh the pieces of paper. There, you've done
calculus.
The sine or square curve gives you the instantaneous voltage plotted
against time. There, the word instantaneous means you have done more
calculus.
The real issue is that you want to turn the voltage into getting work
done. For that you need power. Power is amperes times voltage. But
assuming the same amperes, having more voltage will deliver more
power.
The voltage at any instant of time is like Using an infinitely thin
strip. What good is that? It helps you know how much power you can
generate in that instant, and with some math, you can come up with a
value over time. Weighing the piece of paper gives the same
information.
===
The best way to think of electricity is like water in a hose. Voltage
is equivalent to water pressure. If you think of a water tower, that
creates pressure from gravity. Ther higher you go, the more pressure
you get in the water tower.
You can think of a voltage in the same way, 120 volts can be 120
inches off the ground. The word "ground" here is on purpose because if
the voltage is at ground level, there won't be any flow downhill, no
work done. Curiously the earth also has zero electrical voltage.
Amperage is the volume of water flowing through the hose. The hose
diameter sets the resistance to flow, just like wire size causes
resistance in electricity; resistance will create a pressure/voltage
drop from the inlet to the outlet. With a larger hose, you get less
pressure drop from the inlet of the hose the outlet, in the hose, and
therefore more water flow. Just like wire size in an electrical
circuit.
A tiny bit of water coming out of a high pressure washer can drill a
tiny hole in concrete, like a high voltage with a tiny bit of current
can burn your hand, but to do real damage you want big torrents of
water with high pressure behind it. That will rip your hand into
shreds.
In article <[email protected]>,
[email protected] says...
> See http://en.wikipedia.org/wiki/Mains_electricity and http://www.tpi-thevalueleader.com/rms.html
>
> AC voltage goes from 0 to its peak (120 or 240) and back to 0 (in US, 60 times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).
>
> So what's the real voltage? Not 120, since it's only there an instant. Not 0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.
>
> Your meter can't keep up with changes, so it reads a happy number somewhere in between also.
>
> Many inverters (DC to AC converters) and many types of power supplies, simply chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.
>
> Other applications may have a saw tooth shape.
>
> They both have enough of what's underneath the camel's hump to work.
>
> Your homework assignment for tomorrow is to tell the group what I just said in a way that makes sense.
>
> :)
>
> Looking at the camel's hump, you can see it isn't a simple average since there's less area under the peak than points under the rest of the graph.
>
>
>
>
>
>
I read it twice and didn't see anything you said that didn't make sense.
The only question I'd raise is whether all camel humps follow simple
sine waves or whether some vary and follow the curve of more complex
trig functions. I suspect the latter. However, not having a herd of
camels conveniently nearby I'll have to leave that question to others
who, perhaps, do.
Having done my home workwork for tomorrow, I'm packing to go to
my deer lease; bow hunt a couple of mornings, work, and get ready for
opening weekend (firearms).
:-)
Tex
ok, its been 23 years since I graduated school, so pardon me if I blow
this... even if it is first quarter stuff, but the bottom line is
irregardless of the frequency or voltage, its value at any given time is
its Peak-to-Peak (unless you want RMS) range.
This also explains the difference between AC and DC.
"Square wave" is also known as "pulsating DC".
Do I pass professor?
Troy
[email protected] wrote:
> See http://en.wikipedia.org/wiki/Mains_electricity and http://www.tpi-thevalueleader.com/rms.html
>
> AC voltage goes from 0 to its peak (120 or 240) and back to 0 (in US, 60 times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).
>
> So what's the real voltage? Not 120, since it's only there an instant. Not 0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.
>
> Your meter can't keep up with changes, so it reads a happy number somewhere in between also.
>
> Many inverters (DC to AC converters) and many types of power supplies, simply chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.
>
> Other applications may have a saw tooth shape.
>
> They both have enough of what's underneath the camel's hump to work.
>
> Your homework assignment for tomorrow is to tell the group what I just said in a way that makes sense.
>
> :)
>
> Looking at the camel's hump, you can see it isn't a simple average since there's less area under the peak than points under the rest of the graph.
>
>
>
>
>
>
Close. It's value at any given time is peak. RMS is the quoted voltage. The
peak voltage of a 120 volt line is in the 169 volt range.
"Troy" <[email protected]> wrote in message
news:[email protected]...
> ok, its been 23 years since I graduated school, so pardon me if I blow
> this... even if it is first quarter stuff, but the bottom line is
> irregardless of the frequency or voltage, its value at any given time is
> its Peak-to-Peak (unless you want RMS) range.
> This also explains the difference between AC and DC.
> "Square wave" is also known as "pulsating DC".
> Do I pass professor?
>
> Troy
>
> [email protected] wrote:
> > See http://en.wikipedia.org/wiki/Mains_electricity and
http://www.tpi-thevalueleader.com/rms.html
> >
> > AC voltage goes from 0 to its peak (120 or 240) and back to 0 (in US,
60 times per second). Graph it with voltage and time and it looks like a
camel's hump (sine wave).
> >
> > So what's the real voltage? Not 120, since it's only there an instant.
Not 0, or there would be no voltage. It's somewhere in between since it is
always changing. See the rms voltage article.
> >
> > Your meter can't keep up with changes, so it reads a happy number
somewhere in between also.
> >
> > Many inverters (DC to AC converters) and many types of power supplies,
simply chop off the top of the sine and their electronics square off the
sides as they switch on and off to give the correct frequency. This is
called a square wave.
> >
> > Other applications may have a saw tooth shape.
> >
> > They both have enough of what's underneath the camel's hump to work.
> >
> > Your homework assignment for tomorrow is to tell the group what I just
said in a way that makes sense.
> >
> > :)
> >
> > Looking at the camel's hump, you can see it isn't a simple average
since there's less area under the peak than points under the rest of the
graph.
> >
> >
> >
> >
> >
> >