AN: GuruGram #39

[Don Lancaster]

... is now available for free download as
http://www.tinaja.com/glib/funfield.pdf

It is on fun with fields.

Additional gurugrams at http://www.tinaja.com/gurgrm01.asp
Consulting services available via http://www.tinaja.com/info01.asp

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Active8]

On Fri, 10 Dec 2004 11:39:30 -0800, John Miles wrote:

In article <12lxvb7qtm1b8$.dlg@news.individual.net>,
reply2group@ndbbm.net says...

He means that the rotating field is symmetric and is || to the axis
of rotation. Therefore the flux remains constant throughout the
revolutions.

IOW if you flip the bar magnet around, the field is *not* uniform -
it changes.

True... what confused me is that if a bar magnet is being rotated pole-
over-pole, the field itself is still uniform, but it's easy to observe
its rotation from a fixed point.

It depends on *where* the observer is - on the magnet or not.
--
Best Regards,
Mike

 

[bee]

John Miles wrote:

True... what confused me is that if a bar magnet is being rotated pole-
over-pole, the field itself is still uniform, but it's easy to observe
its rotation from a fixed point. Ergo there *is* such a beast as a
rotating magnetic field.

Still, this is a neat .PDF. Thanks for posting it, Don.

-- jm

But there is ---> no <--- test you could perform on that field that would
let you tell ANY difference between it and a stationary one of equal
uniform strength.

This is the usual place where the homopolar church of the latter day
crackpots types often screw up.

 

[john jardine]

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:it3kr0t8tnmlm5ggfd11ve2jckpbpd465i@4ax.com...
[...]

I did a 3-D calculation to find the voltage gradients in a
electroplating situation back in school. It was fun.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog Info for designers:
http://www.speff.com

Gasp!, you're an 'ard man Spehro .
My favourite heavy calc's in school were figuring how many ciggies I could
buy with my dinner money.
regards
john

 

[Rich Grise]

On Sat, 11 Dec 2004 09:57:35 +0000, John Woodgate wrote:

I read in sci.electronics.design that Rich Grise <rich@example.net
wrote (in <pan.2004.12.11.07.49.07.89260@example.net&gt about 'AN:
GuruGram #39', on Sat, 11 Dec 2004:

And if you have a conductor, with current, with one line of force around
it, does the concept of rotating that line of force (where the conductor
is the axis) even make any sense?

'Lines of force' are imaginary. Rotating something imaginary rarely has
a physical effect.

But if they're imaginary, then what is it that induces the current in the
wire that cuts one?

Thanks,
Rich

 

[bee]

Rich Grise wrote:

On Fri, 10 Dec 2004 16:09:06 -0700, bee wrote:



John Miles wrote:

True... what confused me is that if a bar magnet is being rotated pole-
over-pole, the field itself is still uniform, but it's easy to observe
its rotation from a fixed point. Ergo there *is* such a beast as a
rotating magnetic field.

Still, this is a neat .PDF. Thanks for posting it, Don.

-- jm


But there is ---> no <--- test you could perform on that field that would
let you tell ANY difference between it and a stationary one of equal
uniform strength.

This is the usual place where the homopolar church of the latter day
crackpots types often screw up.

Well, if it doesn't make any difference, then what difference does it make?

Thanks,
Rich

The whole point is that field cutting "lines" do not exist and never did.
The concept is fundamentally bogus.

 

[bee]

John Miles wrote:

In article <41B9E19E.D0C684F2@tinaja.com>, don@tinaja.com says...

... is now available for free download as
http://www.tinaja.com/glib/funfield.pdf

It is on fun with fields.

Additional gurugrams at http://www.tinaja.com/gurgrm01.asp
Consulting services available via http://www.tinaja.com/info01.asp



I don't understand your assertion that "there is no way you can tell if
a perfectly-uniform magnetic field is stationary or rotating."

If I bring a piece of wire into the field, a detectable current will be
induced by a rotating magnetic field, but not a stationary one.

Nope.
Not even wrong.

AC
motors would have a hell of a time working otherwise. Is this one of
those Heisenberg-style trick assertions (e.g., the field's no longer
perfectly-uniform once I couple energy out of it with a conductor)?

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

Read the provided link.
The entire detailed explanation is found in the Feynman lectures among many
other places.

Take a cylindrical magnet and hang it on a string.
Place another cylindrical magnet below it on the same axis.

Rotate the bottom magnet.
The Top one does NOT rotate.

Because you can not tell if a perfectly uniform magnetic field is
stationary or rotating.
General relativity DEMANDS none other.

Again, if you don't like my coverage, see Feynman.
The outcome will remain the same.

-- Don Lancaster

 

[John Woodgate]

I read in sci.electronics.design that Rich Grise <rich@example.net>
wrote (in <pan.2004.12.11.20.08.01.84576@example.net&gt about 'AN:
GuruGram #39', on Sat, 11 Dec 2004:

It seems we're just going to have to sit down and try to reach a
consensus. Who's in charge here, voltage or current? (pun unintended,
but noted.) ;-)

The voltage is there even if the wire is not part of a complete circuit.
Can I do Faraday's equation in ASCII art?

/ / /
| d | |
O e dl = - - | | B dA
| dt| |
/ / /

e is the element of induced voltage
B is the induction
A is the area within which B exists

Some of the puzzles depend on people forgetting that B, A or both may
vary with time.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk