magnetic field

[Uwe Bonnes]

qude <qmdynamics@yahoo.com> wrote:

Supposed you have a certain voltage and resistor values..
for example.. 110 volts and 55 ohms. The current would
then be 2 Ampere. Is there a way to boost the amperage
value to say 5 ampere without changing the voltage nor the
resistance but by doing something to the source??

Accelerate the setup to relativistic speed, then the well known resistance
dilatation gets into effect and allows more current to flow

--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

 

[St. John Smythe]

emma wrote:

What would it take to build a square wave power inverter that
totally eliminate the high frequencies riding in the square wave??

A repeal of some fundamental physical laws. As has already been
explained to you, when you remove the high frequencies, you no longer
have a square wave.

--
St. John

 

[Jan Panteltje]

On a sunny day (28 Jun 2005 18:37:11 -0700) it happened "emma"
<mrandmrsrelativity@yahoo.com> wrote in
<1120009031.592710.272250@g43g2000cwa.googlegroups.com>:

Hi,

I learnt that square waves for examples produced by power
interver has high frequency components.
Any square wave can be thought of as an infinite amount of sine waves.

In practice you will have some harmonics, f, 2f, 3f, 4f etc.
Look up Fourier analysis.

Some inverters make a near square wave, some a modulated pulse width
that is filtered into an approximate sine wave, some just combine some
smaller square waves to make something that looks a bit like a sine.
Some make really good sine waves.

What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz.
120, 180, 240, 300, etc, with varying amplitude.

Is there no way to remove the high frequency
components? How does it affect the load?
Yes, LC filter, but you will lose some power.

If you for some reason need a pure sine wave, get a converter that does that.

Many applications / appliances do not need a real good sine wave, as these
have their own power processing / power supplies - those could handle square
waves even.
In fact in some cases square wave could be beneficial.

 

[Old Man]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1119905485.420796.301280@o13g2000cwo.googlegroups.com...

To create source of magnetic field. You only need wires as
the current passing thru them can create it. The electric
field in the wires is null because there is a cancellation
inside the positive lattice and electrons.

I'd like to build a very strong source of electric field
only.

Moderate potential on a small conducting sphere. Point
of a needle. The sharp edge of a razor blade.

[Old man]

> emma

 

[Jan Panteltje]

On a sunny day (29 Jun 2005 03:57:12 -0700) it happened "emma"
<mrandmrsrelativity@yahoo.com> wrote in
<1120042632.423989.148510@z14g2000cwz.googlegroups.com>:

So the high frequency can be removed. I thought they can't.
How complicated is the LC filter design to remove 100% of
the high frequency component in the square wave?
There are 2 ways, one is a low pass filter, the other a resonant

system.
Low pass is the simplest, it filters out everything above 60Hz
in this case.
It could be as simple as an inductor (L) in series with a capacitor
to ground.
But there are a lot of catches....
For this reason it will almost always be simpler to buy a converter that
already outputs a -reasonable- sine wave, simpler and cheaper then
designing and building one (given some initial likely failures).

First you will have to decide how 'pure' your sine wave should be.
How much power from harmonics should be allowed?

Perhaps it would be better if you specified what you need the
output for (what sort of equipment).

In pure line Alternating Current (sine wave) from power companies.
Is there any high frequency component in the sine wave or is it
pure 100% 60 Hz AC??
It is a pure sine wave, but because of various loads it will carry

some distortion.
For example thyristor controlled devices can cause pulses, some
power companies send extra higher frequency signals over it for control,
some even for internet these days.
A TV with a rectifier will cause flat tops on the sine wave.
So do not expect a very clean wave!
Neither is the voltage always exact.

 

[Jan Panteltje]

On a sunny day (29 Jun 2005 04:55:25 -0700) it happened "emma"
<mrandmrsrelativity@yahoo.com> wrote in
<1120046125.235456.224820@g43g2000cwa.googlegroups.com>:

Perhaps it would be better if you specified what you need the
output for (what sort of equipment).

The output is feed to a resistive coil. I'm analyzing the magnetic
field produced by plotting it in 3D.
Now 'resistive' and 'coil' are 2 things that contradict a bit.

Any coil will behave as an inductor (and have some resistance).
So you can view it as a R in series with an L.
(so Z = R + jwL, were 'w' stands for omega or 2 x pi x frequency).
From this you can see the 'impedance' depends on the frequency applied.

Suppose I have pure AC from the power lines. How would I add
high frequency component to it? Suppose I want to add 300 Hz
to ride on the sine wave, any idea how I can do that??
You have to decouple the 300 Hz from the mains, and also block

the 60 Hz from the driving amp.
At these low frequencies that requires large inductors and capacitors,
not very practical.

--- L---
60Hz ---- --------------------------- load
--- C--- |
300 Hz stop |
parr resonant |
-----
| |
L C
| | 60 Hz stop parallel resonant
-----
|
300Hz

Another. Suppose I feed a function generator to a power amplifier.
Would the power amplifier introduce distortions to the signal
produced in the function generators? What's the worse distortion
that the power amp can introduce to it?

This is the best system, and you could then take 60 Hz from the mains,
attenuate, and simply add 300 Hz from a signal generator, via a resistor
network:


60Hz ---- R------------ amplifier ---------- load
|
300Hz ----R------
|
R
|
//// ground

We have seen that the 'impedance' of the coil you use is very low
at low frequencies (practically near its resistance in Ohms), while
at higher frequencies it will have a higher impedance.

The amplifier should be able to drive the low impedance, say if the
coil is 4 Ohm, and the amplifier can drive 4 ohm speakers this should
be possible.
You will have to keep the output amplitude below clipping to keep a sine wave.
At the 300Hz, what the impedance is, depends on the inductance of the coil,
that is set by the number of turns and if there is some metal core.
How much current you can drive into the coil at frequency f is set by
the impedance and the peak to peak undistorted output from the amplifier
you use.
Here is a power amp I use for experiments, it is quite rigid and protected
against overload (within reason).
http://panteltje.com/panteltje/amplifier/

 

[CWatters]

"Uwe Bonnes" <bon@elektron.ikp.physik.tu-darmstadt.de> wrote in message
news:d9tjoh$sts$1@lnx107.hrz.tu-darmstadt.de...

qude <qmdynamics@yahoo.com> wrote:

Supposed you have a certain voltage and resistor values..
for example.. 110 volts and 55 ohms. The current would
then be 2 Ampere. Is there a way to boost the amperage
value to say 5 ampere without changing the voltage nor the
resistance but by doing something to the source??

Accelerate the setup to relativistic speed, then the well known resistance
dilatation gets into effect and allows more current to flow

Yes.

If we were talking about 110V DC (which you probably aren't) you could built
a DC-DC converter to turn the 110V into say 275V.

The output current would be 275/55 = 5A
The input current would be 5 * 275/110 = 12.5A (if you ignore losses).

In practice the imput current is likely to be nearer 16A because DC-DC
converters don't have 100% power efficiency.

If you are talking about AC the priciple is the same but the design is more
complex. 110-220V converters are easy to obtain so achieving 4A (=220/55) is
easy.

 

[St. John Smythe]

Manny wrote:

I have a 12 volts 100 watts DC halogen lamp. From P=VI,
I (current) = P/V = 100/12 = 8.33 Ampere

I used a multi-meter to check the resistance of the
lamp. It is 0.7 ohms.

Now since it's 12 volts. From V=IR, I=V/R=12/0.7= 17A.

How come it's 17A when the calculated one in the first
sentence is only 8.33A?? Which is the right one?

When you use a multi-meter to test the resistance
in ohms of the lamp, is the reading accurate?

Yes, at room temperature. When the filament gets white-hot, its
resistance is significantly lower.
--
St. John

 

[St. John Smythe]

St. John Smythe wrote:

Yes, at room temperature. When the filament gets white-hot, its
resistance is significantly lower.

D'oh! HIGHER! I meant higher.
--
St. John

 

[Jan Panteltje]

On a sunny day (29 Jun 2005 07:32:09 -0700) it happened "emma"
<mrandmrsrelativity@yahoo.com> wrote in
<1120055529.644200.213390@g47g2000cwa.googlegroups.com>:

So you can view it as a R in series with an L.
(so Z = R + jwL, were 'w' stands for omega or 2 x pi x frequency).
From this you can see the 'impedance' depends on the frequency applied.

When I say resistive coil. It's not one load. I used an electric
bulb in the output.. then the coil is put in series to it. The
coil has reading of 1.7 ohms.

Do you know of a program where I can input the waveforms (i.e.
sine or square and its micropulsations) and it can output or plot
the magnetic field of the waveforms in 3D? I have to do it manually
and need something for comparison.
I am still a bit puzzled to what you are trying to do.

Here are my questions:
If you say 'magnetic field' what field are you referring to,
the one from the coil? So then you have a probe, and measure everywhere
near and in the coil the magnetic field, and plot that?
I am sure there are examples of solenoid (single layer coils) with field
lines on the net, search via google:
solenoid field lines
I find many many hits,
here
http://www.bfafairfax.com/~pfeiffer/concphys/EandM/magnetism.html
The field will be symmetrical if you coil is, so 3D = 2D

The amplifier should be able to drive the low impedance, say if the
coil is 4 Ohm, and the amplifier can drive 4 ohm speakers this should
be possible.

That means I can't use any 100 ohm lamp in the output of the speakers.
But you could use a simple trick, add a 3 Ohm resistor is series with the

coil, and use an amplifier that can drive 4 Ohm.
This way the amp will not be overloaded.

amplifier --- 3 Ohm -- 1 Ohm coil -- ground

I can't find any AC resistor 110 volts at electronic stores. The
most they have is a 1 watt resistor for used in circuit. What's the
other names for AC resistors? Are their power amplifers that don't
have resistance limit in their output?
Resistors behave the same for AC and DC (except from very high frequencies,

many MHz, where they act like an inductor depending upon their construction).

I won't build the amplifier. I have wasted so much time constructing
pcb, circuit, soldering for a function generator and variable power
inverter and it's only up to 9 khz. I want something as large as 10
megahertz. Can commercial function gen create very clean sine wave?
What's your function gen?
I designed my own.

Now I use an FPGA (programmable gate array) with a fast DA converter.
You calculate the waveform for say 1024 points, upload to the (very
fast) FPGA internal RAM, and then program the FPGA so it outputs at the
right speed.
Or just program the required pulse sequence (in Verilog).
You are limited by the clock speed divided by the number of samples you want.
64 samples per period at 10MHz output would require a 640 MHz clock!
Mine does not go that fast (and and neither the DA).
And 64 samples is not exactly a 'pure' sine wave.
If you just want the sine waves, use any LC signal RF generator.
If you want only frequencies in the audio range, use the PC sound card,
and a good sound editor.
In the past I have made waveforms by writing a simple BASIC program,
calculate for example some values, and write it to a raw file (binary
sound file). Then most sound editors will be able to make a wave file.

If all else fails get a good RF generator from ebay?
While you are at it get an oscilloscope, and all this is difficult to do
without being able to see the waveforms (even if just to check nothing
clips).
A 10MHz scope should be dirt cheap on ebay.

About the power amp. I want to buy a commercially available one.
Are older transistor based solid state circuit better or worse
compared to modern ic based power amp in preventing distortions
in the waveform sent from the function gen input?
If you say 'I want 10MHz' then you have a problem.

Please also state the amount of power you want (at that frequency).
The other thing is how will you detect the magnetic field at 10MHz?
You can detect LF fields very good with an old playback head, but
not in the MHz range.

What do you call power amps where it is not used for audio only
but also for function gen amplification??
I would call a 10MHz power amp a power amplifier with 10MHz bandwidth....

I need to get very clean source so I can prevent any contaminations
of frequencies in the output.

One way of doing that is using an amplifier with as narrow a bandwidth
as possible, for example if you want 10kHz, a 10MHz wide amp will
only add unwanted stuff!

I am still not 100% clear on what you want to do, how will you measure the
magnetic field?

 

[CWatters]

"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:1120059038.54704b6708a8757ecce7db46932843db@teranews...

I am still a bit puzzled to what you are trying to do.

...and why experiment at 110V when say 9V would be a lot safer?

 

[me]

"CWatters" <colin.watters@pandoraBOX.be> wrote in
news:Utwwe.132966$si1.6974535@phobos.telenet-ops.be:

"Uwe Bonnes" <bon@elektron.ikp.physik.tu-darmstadt.de> wrote in message
news:d9tjoh$sts$1@lnx107.hrz.tu-darmstadt.de...
qude <qmdynamics@yahoo.com> wrote:

Supposed you have a certain voltage and resistor values..
for example.. 110 volts and 55 ohms. The current would
then be 2 Ampere. Is there a way to boost the amperage
value to say 5 ampere without changing the voltage nor the
resistance but by doing something to the source??

Accelerate the setup to relativistic speed, then the well known
resistance dilatation gets into effect and allows more current to
flow

Yes.

If we were talking about 110V DC (which you probably aren't) you could
built a DC-DC converter to turn the 110V into say 275V.

um, that's changing the source...

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

 

[Old Man]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1120009031.592710.272250@g43g2000cwa.googlegroups.com...

I learnt that square waves for examples produced by power
interver has high frequency components. What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz. Is there no way to remove the high frequency
components? How does it affect the load?

You can get an estimate of the high frequency component
from the rise and fall times of the "square" wave. A low pass
LC filter will reduce the high frequencies. Expensive.

[Old Man]

emma

 

[Old Man]

"Tm" <smiller615@nospamcast.net> wrote in message
newsI6dnfn9gcjPvV_fRVn-iw@comcast.com...

"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:42C1FE4B.50666504@hate.spam.net...
emma wrote:

Hi,

I learnt that square waves for examples produced by power
interver has high frequency components. What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz. Is there no way to remove the high frequency
components? How does it affect the load?

Bandpass filter.

Low Pass will do it. But you will need more than a 110 volt square wave to
start with if you expect to get a 110 volt sine.

No loss in RMS power.

In principle (R_ series = 0, R__parallel = infinite), an LC
low pass filter is lossless.

[Old Man]

TM

 

[Bob Myers]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1120042632.423989.148510@z14g2000cwz.googlegroups.com...

So the high frequency can be removed. I thought they can't.
How complicated is the LC filter design to remove 100% of
the high frequency component in the square wave?

I think you're still missing the point. A square wave has
"high-frequency components" simply by virtue of being
a square wave. Take those away, and it's not a square
wave any more. Take ALL of them away, except for the
base, or what's called the "fundamental" frequency, and you
have a pure sine wave.

Basically, you get additional components in ANY signal
in which something is changing more rapidly than it would
in the case of a sine wave at that frequency. (That's a terrible
oversimplification, but I'm hoping you'll see the point from it.)
In short, if you see any sort of "wave" with "sharp edges,"
it has high-frequency components.

In pure line Alternating Current (sine wave) from power companies.
Is there any high frequency component in the sine wave or is it
pure 100% 60 Hz AC??

A sine wave is a "pure" signal in the sense that it exists, or
has components, only at one specific frequency. A 60 Hz
sine wave is a "pure 60 Hz tone," in more musical terms.


Bob M.

 

[John Fields]

On 28 Jun 2005 23:33:20 -0700, "qude" <qmdynamics@yahoo.com> wrote:

Supposed you have a certain voltage and resistor values..
for example.. 110 volts and 55 ohms. The current would
then be 2 Ampere. Is there a way to boost the amperage
value to say 5 ampere without changing the voltage nor the
resistance but by doing something to the source??

---
No.

--
John Fields
Professional Circuit Designer

 

[John Fields]

On Wed, 29 Jun 2005 10:30:28 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (28 Jun 2005 18:37:11 -0700) it happened "emma"
mrandmrsrelativity@yahoo.com> wrote in
1120009031.592710.272250@g43g2000cwa.googlegroups.com>:

Hi,

I learnt that square waves for examples produced by power
interver has high frequency components.
Any square wave can be thought of as an infinite amount of sine waves.
In practice you will have some harmonics, f, 2f, 3f, 4f etc.
---

No. A _square_ wave is composed of an infinite series of _odd_
harmonics.

--
John Fields
Professional Circuit Designer

 

[Uncle Al]

emma wrote:
[snip]

Well. Let's just say that I need to know all the magnetic field
configurations of all kinds of signals... square waves with high
freq components, triangular waves, sine waves because I want to
build a radio or other circuit powered by induction (without
contact). For example, a radio put near a computer monitor that
can power itself (by induction).
[snip]

"Best efforts will not substitute for knowledge," W. Edwards Deming.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

 

[Dave]

"St. John Smythe" <UndisclosedRecipient@privacy.net> wrote in message
news:d9ub8i$q31$2@n4vu2.n4vu.com...

St. John Smythe wrote:
Yes, at room temperature. When the filament gets white-hot, its
resistance is significantly lower.

D'oh! HIGHER! I meant higher.
--
St. John

Not only that, but the filament is a COIL, which has inductive reactance to
AC. Your multimeter uses DC to measure resistance. Not the same. Trust
the calculations. They tell the truth.

Dave
db5151@hotmail.com

 

[CWatters]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1120083238.071640.207610@g49g2000cwa.googlegroups.com...

I want to build a radio or other circuit powered by induction
(without contact). For example, a radio put near a computer
monitor that can power itself (by induction).

Can I recommend you try placing an ordinary radio next to a computer first.
Try picking up a selection of different stations.