magnetic field

[Joe Strout]

In article <pan.2005.05.20.15.34.51.40159@example.net>,
Rich Grise <richgrise@example.net> wrote:

I did read a story or essay, where the guy actually treated a tether
seriously, and he did some numbers, and they were mind-boggling...
Eventually, by the time they
had 22,500 miles of Kevlar unreeled, there was so much tension on it
that it had to be like thousands of feet thick.

You need to read some of the more recent studies. There are materials
much better than kevlar, though none quite good enough yet to make a
space elevator practical -- but progress towards that material is being
made pretty rapidly, and this is no longer an idea to be dismissed
lightly. At least one company is actively pursuing it (and is now
working with NASA to spur the development of appropriate climbers via
the Centennial Challenges program).

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'

 

[SioL]

"Rich Grise" <richgrise@example.net> wrote in message newsan.2005.05.20.15.34.51.40159@example.net...

I did read a story or essay, where the guy actually treated a tether
seriously, and he did some numbers, and they were mind-boggling. To do it,
he started with a BIG geostationary satellite, and started feeding
tether lines from the near and far sides simultaneously, so that they'd
balance. But at any place except that orbit, the tethers are subjected
to tidal forces - they're being pulled on. Eventually, by the time they
had 22,500 miles of Kevlar unreeled, there was so much tension on it
that it had to be like thousands of feet thick. This is one of the
problems they have with cables to deep-diving submersibles - the cable
has to be made neutrally buoyant, because otherwise it can't support
its own weight.

http://seattlepi.nwsource.com/business/221576_liftport26.html

I wonder if these guys are serious or perhaps just using publicity to
sell their nanotubes for other purposes.


--
Siol
------------------------------------------------
Rather than a heartless beep
Or a rude error message,
See these simple words: "File not found."

 

[bz]

"Robert Clark" <rgregoryclark@yahoo.com> wrote in
news:1116608652.324176.280290@g44g2000cwa.googlegroups.com:

You would locate the launcher at the gigawatt scale at very dry areas.
While transmission lines typically carry hundreds of kilovolts some do
go up to a million volts.
Using voltages in the hundreds of kilovolt range, power stations
already exist that transmit gigawatts of power over hundreds of
kilometers:

I haven't found any 1 MV transmission lines. 450 kV is the highest I saw,
but I did find some cool pictures of arcs and sparks.

http://teslamania.delete.org/frames/longarc.htm

Also some real neat looking pictures of the results of 'quarter shrinkers'.
Which use very high pulsed magnetic fields to shrink coins.





--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+sp@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Joe Strout]

In article <nZoje.12222$F6.2557809@news.siol.net>,
"SioL" <Sio_spam_L@same.net> wrote:

http://seattlepi.nwsource.com/business/221576_liftport26.html

I wonder if these guys are serious or perhaps just using publicity to
sell their nanotubes for other purposes.

They are very serious. Any selling of the nanotubes for other purposes
is just to fund further development of the space elevator.

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'

 

[Art]

Designed with isolation between the chassis reference and any externally
accessable connectors. Voltage you are measuring ar the avio reference is
probably a result of static charge induced when the set in energized.
"siliconmike" <siliconmike@yahoo.com> wrote in message
news:1116664802.092333.281110@g14g2000cwa.googlegroups.com...

I just bought a new TV and found

1. it had no earthing pin in its power cable (only Phase and Neutral
were there)

2. its audio GND (accessible from RCA connector) showed me presence of
voltage when I touched a screw-driver-cum-mains-tester to it.

3. I tried to touch the audio GND, but did not get a shock.


First, why was the TV GND floating (meaning, not earthed) ?

Can I safely connect my PC audio output to TV audio input ?

What if I manually earthed the TV GND ?

Thanks
Mike

 

In article <a9Oie.79$25.17760@news.uchicago.edu>,
mmeron@cars3.uchicago.edu wrote:

In article <1116446501.892789.156400@f14g2000cwb.googlegroups.com>,
"tadchem" <thomas.davidson@dla.mil> writes:

Charles Jean wrote:

snip

"There are known knowns. These are things that we know we know.
There are known unknowns. That is to say, there are some
things that we know we don't know. But there are also unknown
unknowns. These are things we don't know we don't know."
-Secretary of Defense Donald Rumsfeld

If Rummy really said this,

He did.

I dropped my jaw to hear this from a dais located in Washington D. C.
He also did other things that were fraught with intelligence.

then he is much more widely read than I
would have believed. This is a variation of a quotation from Lady
Burton, attributed as an 'Arabian Proverb':
"Men are four:
He who knows not and knows not he knows not, he is a fool--shun him;
He who knows not and knows he knows not, he is simple--teach him;
He who knows and knows not he knows, he is asleep--wake him;
He who knows and knows he knows, he is wise--follow him!"

Yep. Closer to home, note that the first category above is endowed
with what we (meaning sci.physics regulars) refer to as "second order
ignorance", which is the characteristic of many of our cranks.

Anyway, Rummy did say this and many seemingly intelligent people
jumped on this as a "dumb statement", not realizing that it was their
own stupidity they were thus proclaiming.

Yes, these types fixed his behaviour. Now anything that is decided
or accomplished using brains, as they should be used, will not
be documented. I drove down to Bethesda a couple of years ago
and kept looking for the toll booth where everybody had to hand
in his/her organ that contains common sense.

I got that book. I've read the first two chapters. I spent my
dreamtime last night editing my mental data base. I'm so tired.

/BAH

Subtract a hundred and four for e-mail.

 

[Fred Abse]

On Wed, 11 May 2005 13:03:09 +0200, Michael Redmann wrote:

I'm not sure burn-in is dependent on refresh rates. I think that at any
refresh rates the screen phosphor is "illuminated" the same amount of time
(more or less) by electron beam. Perhaps the different types of phosphor
(monitor vs. TV) have different decay rates and that's the reason for TVs
to tend to burn-in.

You may well be right. I've not noticed industrial monitors running at
15KHz x 60Hz burn any worse than those running at 31.5KHz x 70-something
Hz. They both burn noticeably in a couple of years. It's down to watts per
square meter, I guess. Same light output, same power density, same
degradation.

Are TV phosphors different from monitor phosphors? TVs don't appear to
burn as much, but they generally don't run 24/7 on stationary patterns,
and the raster fully fills the screen area, whereas monitors are usually
underscanned slightly. It may just be less noticeable.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)

 

[Vidar Lřkken]

albertleng@gmail.com wrote:

Just a very basic question:

Can anyone share with me what's the benefit of using transistor as an
electrical relay compared to mechanical relay when the incoming signal
is from a computer?

Is it related to pricing, input voltage/current, power rating and etc?

A digital IO typically can't drive a mechanical relay directly. A
transistor is needed to amplify the current and/or the voltage, so that
the relay can operate. Also, look at optocouplers. They're often used.
So it ain't a benefit. It is a must. No fuckin' way you can handle a
mechanical relay from a computer...


--
MVH,
Vidar

www.bitsex.net

 

[Rich Grise]

On Sat, 21 May 2005 01:40:02 -0700, siliconmike wrote:

I just bought a new TV and found

1. it had no earthing pin in its power cable (only Phase and Neutral
were there)

2. its audio GND (accessible from RCA connector) showed me presence of
voltage when I touched a screw-driver-cum-mains-tester to it.

3. I tried to touch the audio GND, but did not get a shock.


First, why was the TV GND floating (meaning, not earthed) ?

Because it's chassis ground, or signal common, neither of which is Earth
ground. (obviously, because the set is fully isolated and has no Earth
pin).

Can I safely connect my PC audio output to TV audio input ?

Probably. But why?

What if I manually earthed the TV GND ?

Don't. It will cause ground loops, and introduce problems that you
don't have now. This is an entire subject of study - try
http://www.google.com/search?q=earth+ground+and+ground+loops

Thanks
Mike

You're welcome.

Cheers!
Rich

 

[Rich Grise]

On Sat, 21 May 2005 07:27:32 -0400, Art wrote:

Designed with isolation between the chassis reference and any externally
accessable connectors. Voltage you are measuring ar the avio reference is
probably a result of static charge induced when the set in energized.

More likely capacitively coupled or ordinary electromagnetic induction a
la antenna.

Cheers!
Rich

"siliconmike" <siliconmike@yahoo.com> wrote in message
news:1116664802.092333.281110@g14g2000cwa.googlegroups.com...
I just bought a new TV and found

1. it had no earthing pin in its power cable (only Phase and Neutral
were there)

2. its audio GND (accessible from RCA connector) showed me presence of
voltage when I touched a screw-driver-cum-mains-tester to it.

3. I tried to touch the audio GND, but did not get a shock.


First, why was the TV GND floating (meaning, not earthed) ?

Can I safely connect my PC audio output to TV audio input ?

What if I manually earthed the TV GND ?

Thanks
Mike

 

[w_tom]

First some definitions and concepts. Then some simple
experiments.

Your are confusing earth ground with something called safety
ground. Your TV has no safety ground connection because a
third ground inside the TV is isolated - a floating ground. A
voltage difference between a floating ground and safety ground
is undefined. It may or may not harm you if you touch both
simultaneously.

In the meantime, anything conductive outside of that TV must
be galvanically isolated from floating ground. Isolated does
not mean no electrical conductivity. Isolated means minimal
electrical connection.

Two tests for sufficient human safety. First, plug the TV
into a working (and pre-tested) GFCI outlet. Connect a jumper
cable from that audio ground to the safety ground (ie a screw
holding the wall receptacle cover plate). This test should
not trip the GFCI. Some current will pass from that audio
ground into wall receptacle. Current must be so low as to not
trip GFCI.

Second, measure that leakage current using the meter set for
AC current. Measure well less than 150 microamps (0.15
milliamps) from audio ground to wall receptacle 'safety
ground'. Some leakage current should be measured. Current so
low as to not threaten human life and not trip the GFCI.
Galvanic isolation does not mean zero current. It means
minimal leakage current.

BTW, the safety ground on wall receptacle does nothing for
lightning protection. Wall receptacle does not provide an
earthing ground for so many reasons. The safety ground wire is
too long (well over 10 feet), has too many splices, has too
many sharp bends, is bundled with other non-earthing wires,
etc. Earthing is not found at a wall receptacle for so many
above reasons and due to excessive wire impedance. Earthing
for lightning protection means a short wire directly to single
point earth ground; which is different from safety ground,
floating ground, audio ground, and motherboard ground inside a
computer. Don't confuse these many grounds even though some
may be interconnected.

siliconmike wrote:

I just bought a new TV and found

1. it had no earthing pin in its power cable (only Phase and Neutral
were there)

2. its audio GND (accessible from RCA connector) showed me presence of
voltage when I touched a screw-driver-cum-mains-tester to it.

3. I tried to touch the audio GND, but did not get a shock.

First, why was the TV GND floating (meaning, not earthed) ?

Can I safely connect my PC audio output to TV audio input ?

What if I manually earthed the TV GND ?

Thanks
Mike

 

[R. Steve Walz]

Vidar Lřkken wrote:

albertleng@gmail.com wrote:
Just a very basic question:

Can anyone share with me what's the benefit of using transistor as an
electrical relay compared to mechanical relay when the incoming signal
is from a computer?

Is it related to pricing, input voltage/current, power rating and etc?

A digital IO typically can't drive a mechanical relay directly. A
transistor is needed to amplify the current and/or the voltage, so that
the relay can operate. Also, look at optocouplers. They're often used.
So it ain't a benefit. It is a must. No fuckin' way you can handle a
mechanical relay from a computer...

--
MVH,
Vidar

www.bitsex.net
----------------

Wrongo! Many relay coils are made to operate on a volt or two, and
they are made for computers.

-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public

 

In article <GeidncrxZrNTuBLfRVn-3w@rcn.net>, jmfbahciv@aol.com writes:

In article <a9Oie.79$25.17760@news.uchicago.edu>,
mmeron@cars3.uchicago.edu wrote:
In article <1116446501.892789.156400@f14g2000cwb.googlegroups.com>,
"tadchem" <thomas.davidson@dla.mil> writes:

Charles Jean wrote:

snip

"There are known knowns. These are things that we know we know.
There are known unknowns. That is to say, there are some
things that we know we don't know. But there are also unknown
unknowns. These are things we don't know we don't know."
-Secretary of Defense Donald Rumsfeld

If Rummy really said this,

He did.

I dropped my jaw to hear this from a dais located in Washington D. C.
He also did other things that were fraught with intelligence.

Yep.

then he is much more widely read than I
would have believed. This is a variation of a quotation from Lady
Burton, attributed as an 'Arabian Proverb':
"Men are four:
He who knows not and knows not he knows not, he is a fool--shun him;
He who knows not and knows he knows not, he is simple--teach him;
He who knows and knows not he knows, he is asleep--wake him;
He who knows and knows he knows, he is wise--follow him!"

Yep. Closer to home, note that the first category above is endowed
with what we (meaning sci.physics regulars) refer to as "second order
ignorance", which is the characteristic of many of our cranks.

Anyway, Rummy did say this and many seemingly intelligent people
jumped on this as a "dumb statement", not realizing that it was their
own stupidity they were thus proclaiming.

Yes, these types fixed his behaviour. Now anything that is decided
or accomplished using brains, as they should be used, will not
be documented.

Indeed. Would be dangerous to act otherwise.

I drove down to Bethesda a couple of years ago
and kept looking for the toll booth where everybody had to hand
in his/her organ that contains common sense.

))

I got that book. I've read the first two chapters. I spent my
dreamtime last night editing my mental data base. I'm so tired.

Well, let me know what you think, when you finish.

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

 

[Echo]

I would purchase a 1/4 stereo headphone plug remove the sheath and break off
the terminals so they won't contact anything. You can then put a blob of
silicon over the contacts so they don't touch anything. Then if you need the
input you can simply unplug the jack. Else try a wooden golf T.


<Robijean@hotmail.com> wrote in message
news:1115339581.434380.179780@z14g2000cwz.googlegroups.com...

I have a public amplifier with one input 1/4 female connector that I
want to condemn so that nobody will be able to connect a male connector
into it.
But the problem is that I can not take this female connector off the
amplifier.
Is there any secure/appropriate way to condemn the female connector?
I do not want to put some glue or silicon inside the hole...
Thanks for any suggestion.

 

[Vidar Lřkken]

R. Steve Walz wrote:

----------------
Wrongo! Many relay coils are made to operate on a volt or two, and
they are made for computers.

Ahh, maybe just I that haven't came across them yet... I either use
transistors to drive DC low-voltage load, or, for light bulbs and so, a
solid state relay, and for some stuff, I let the solid state relay feed
a mechanical heavy duty relay, esp. when controlling engines.

Besides, I'm sceptical to hook up impedances to a computer...

-Steve

--
MVH,
Vidar

www.bitsex.net

 

[John Miller]

siliconmike wrote:

Right, thats understood. Now since the TV has 2000W exceptionally good
audio amplifier, I would like to connect audio out from my PC to audio
in of TV.

Has the brand of the TV been mentioned?

--
John Miller
email domain: n4vu.com; username: jsm(@)

 

[George Dishman]

<rgregoryclark@yahoo.com> wrote in message
news:1116754002.635313.48190@g43g2000cwa.googlegroups.com...
<snip>

Eliminate t from these two equations to get 2*a*s=v^2. If you want v to
equal orbital velocity, about 8000m/s, then a*s = 32*10^6. If you want
s , which will be the length of the cable, to be 100,000m, then a = 320
m/s^2, about 32 g's (using g as approx. 10 m/s^2). For this
acceleration you would want the payload just to be cargo. The purpose
of this is to make launches of megakilo payloads possible at low cost
remember. Electronics can easily be hardened to withstand this
acceleration. Note also the time would only be t = v/a = 8000/320 = 25
seconds.
Or you could make the distance be 5 times longer, making the cable 5
times heavier, and the acceleration would be 6.4 g's. This is probably
within the range humans can take for a few minutes:

For goodness sake Bob, try to inject some
common sense into your ideas. It isn't within
the tensile strength of the cable and we have
no engine capability that could produce the
thrust needed to accelerate the payload plus
the mass of the cable at that rate no matter
how much electrical power you give it.

Humans are irrelevant, try working out the
numbers to launch Cassini using your method.

George

 

In article <jeSje.115$25.24310@news.uchicago.edu>,
mmeron@cars3.uchicago.edu wrote:

In article <GeidncrxZrNTuBLfRVn-3w@rcn.net>, jmfbahciv@aol.com writes:
In article <a9Oie.79$25.17760@news.uchicago.edu>,
mmeron@cars3.uchicago.edu wrote:
In article <1116446501.892789.156400@f14g2000cwb.googlegroups.com>,
"tadchem" <thomas.davidson@dla.mil> writes:

Charles Jean wrote:

snip

"There are known knowns. These are things that we know we know.
There are known unknowns. That is to say, there are some
things that we know we don't know. But there are also unknown
unknowns. These are things we don't know we don't know."
-Secretary of Defense Donald Rumsfeld

If Rummy really said this,

He did.

I dropped my jaw to hear this from a dais located in Washington D. C.
He also did other things that were fraught with intelligence.

Yep.

then he is much more widely read than I
would have believed. This is a variation of a quotation from Lady
Burton, attributed as an 'Arabian Proverb':
"Men are four:
He who knows not and knows not he knows not, he is a fool--shun him;
He who knows not and knows he knows not, he is simple--teach him;
He who knows and knows not he knows, he is asleep--wake him;
He who knows and knows he knows, he is wise--follow him!"

Yep. Closer to home, note that the first category above is endowed
with what we (meaning sci.physics regulars) refer to as "second order
ignorance", which is the characteristic of many of our cranks.

Anyway, Rummy did say this and many seemingly intelligent people
jumped on this as a "dumb statement", not realizing that it was their
own stupidity they were thus proclaiming.

Yes, these types fixed his behaviour. Now anything that is decided
or accomplished using brains, as they should be used, will not
be documented.

Indeed. Would be dangerous to act otherwise.

This irritates the hell out of me. How am I supposed to learn
stuff if those who have the knowledge can't make it available?
Politics have already sewn distribution of certain doors shut.
When will the intelligentsia finish with mundane things like
science and personal finances?

Imposing this kind of behaviour is extremely dangerous because
one of the things that these idiots jumped on was a memo
where he asked that people speculate about scenarios that
could happen and backup plans if they did occur.

I drove down to Bethesda a couple of years ago
and kept looking for the toll booth where everybody had to hand
in his/her organ that contains common sense.

))

I personal crank theory is that Leonardo was correct about
this sense organ and the fact that none can be found proves it.

I got that book. I've read the first two chapters. I spent my
dreamtime last night editing my mental data base. I'm so tired.

Well, let me know what you think, when you finish.

I've already used it. I have a criticism but
I wish to wait until I finish because there had to be
a purpose the author organized it the way he did.

So far, most of what he has written, I've known instinctively
but could never describe in English ASCII. I'm blessing that
man's mother because he's done this work for me.

/BAH

Subtract a hundred and four for e-mail.

 

[w_tom]

If wire is grounded via computer and soundcard (a common
mode connection), then no static problem exists. None.

Static is not created by the TV. Voltage leakage from a
floating ground, as described earlier, may be created by the
TV. That leakage must be so low as to not harm humans, which
means that leakage is too low to harm electronics. If
worried, then make the connections before powering computer
and TV. A redundant layer of protection.

Earlier noted was that a defective TV (galvanic isolation
failed) might conduct current through you when you touch both
audio ground and safety ground simultaneously. But then this
is what those two experiments do. They confirm the defect
does not exist.

I don't know if you have a GFCI (or RCD) in India to perform
that first test.

siliconmike wrote:

Right, thats understood. Now since the TV has 2000W exceptionally good
audio amplifier, I would like to connect audio out from my PC to audio
in of TV.

As I understand, your mentioned example current (0.15 mA) would flow
from the TV signal ground to the Sound Card GND tracks, then to the
mother board GND tracks, then to the POWER SUPPLY gnd wire, then to the
WALL OUTLET safety GND..
(PC has earth pin)

Although this current is too small, I presume it is not worth taking a
risk. Moreover, if some static phenomenon occurs in the TV, it might
damage the PC!

 

[N:dlzc D:aol T:com (dlzc)]

Dear Robert Clark:

"Robert Clark" <rgregoryclark@yahoo.com> wrote in message
news:1116780175.365218.161060@g44g2000cwa.googlegroups.com...
....

The point of this thread is the savings in power
you would get by using a lifter thruster method.
Look at the table near the bottom on this page:

Lifter Theory.
http://jnaudin.free.fr/html/lf­theory.htm

The last line in this table labled
Thrust(g)/Power(W) ratio gives the weight that
could be lifted for given power with the air
density available at ground level. It is given as
0.509, or about 2 to 1 for power in watts
required to lift a weight in grams.

Lift that is not countered in any sense by "V^2" of drag through
the atmosphere. An atmosphere that becomes increasingly
conductive as it is heated, further reducing your thrust.

This is a waste of time and effort. Rocket engines are more
efficient than 50% at turning power into velocity, or even in
sustaining position.

David A. Smith