magnetic field

And I thought Checkmate was being funny. ;-)

Reply to
No Spam
Loading thread data ...

Sod that, I overtake the buggers. Never been pulled yet.

Reply to
Clint Sharp

More like symmetric eigen decomposition done graphically. It just happens that the matrix it operates on is a 2D stress tensor. But you can still diagonalize it (ie represent shear as tension only).

Your hopes may be elevated, sadly. Though I'm not sure.

They also are for rank 2 tensors aren't they?

-Ed

Reply to
E. Rosten

Isn't it assymetrical, with a constant current producing a constant magnetic field?

Reply to
Tom Del Rosso

in article p_c6d.642262$ snipped-for-privacy@bgtnsc04-news.ops.worldnet.att.net, Tom Del Rosso at snipped-for-privacy@att.net.invalid wrote on 9/28/04 5:41 AM:

It is only assymmetrical because there are no magnetic charges. Magnetic charge does not appear Maxwell's equations. The symmetries or lack of them show up more strongly in the four-vector relativistic formulations.

Bill

Reply to
Repeating Rifle

IIRC, magnetic charges (known also as magnetic monopoles) are theoretically possible (according to some physicists). This leads to the very minor addition to Maxwell's Equations that

div B = m

which is analogous to

div D = rho

However, magnetic monopoles are thought to exist at such high energies that can never be observed.

-Ed

Reply to
E. Rosten

And so with any motion related phenomena. Person A is on a flatbed rail car. Just as the train passes a road crossing A tosses a tennis ball straight up to a height h and catches it as it comes back down. Person A calculates the distance the ball has traveled as 2h. Person B is stopped at the crossing watching the train go by and sees the ball as moving through a parabolic arc. He calculates that the ball has moved a distance through space equal to the length of the parabola, greater than 2h. The two observers arrive at completely different values and describe completely different trajectory geometries. So, how far did the ball REALLY move through space and what was its ACTUAL trajectory? What was the ball's ACTUAL kinetic energy in the direction of the train's motion? A says zero, B says it's half the mass of the ball times the velocity of the train squared. Either the ball has energy or doesn't - who's right. The problem is that even notions as simple as "trajectory" or "kinetic energy" aren't entities in themselves but arise as part of a relationship between the motion of observer with observed.

Perion

Reply to
Perion

On Mon, 27 Sep 2004 17:01:03 -0500, No Spam put forth the notion that...

That was the idea, anyway... tough crowd.

Reply to
Checkmate

Kevin said, "a magnetic field is created as an electric field changes, and an electric field is created as a magnetic field changes".

I thought a magnetic field is proportional to the current, not the change in current. Whereas an induced current is proportional to the rate of change of magnetic field. That's the assymetry I refered to, but I'm seeking clarification. Am I wrong or are we both right?

Reply to
Tom Del Rosso

In a nutshell, a magnetic field is a virtual photon field where all their spins are aligned. It is impressed on the vacuum and the photons aren't really there at all (just like electrical charge is the emission and absorption of virtual photons). Think of it as a spin field impressed on the vacuum that makes any virtual photons that appear be aligned in a specific way.

Cheers!

Sir Charles W. Shults III, K. B. B. Xenotech Research

321-206-1840
Reply to
Sir Charles W. Shults III

If you think about it, you'll see that a constant current is equivalent to a constant RATE OF CHANGE of charge at two places.

Sylvia.

Reply to
Sylvia Else

I was told that Einstein showed that there is not actually any magnetic field and that what we see happen in motors etc. can be explained by relativistic effects. Maybe this is related to this thought experiment? I didn't get any further explanation, and I never did look into it any. Hang on...

[from a google on: einstein "no magnetic field"

formatting link
Nobody Loves A Transformer, Part 2: Wire Again by Brian McGinty

...it took Albert Einstein to figure them out. Stationary electrons don't have a magnetic field. A single electron moving through empty space doesn't have a magnetic field. Two electrons moving together, still no magnetic field.

When electrons move relative to each other - towards each other, away from each other, past each other - a magnetic field appears out of nowhere. In fact, Einstein discovered the magnetic field is just the electric field as viewed through changing frames of reference. Considered by many to be quite a sharp guy, ...

j
Reply to
operator jay

For sure, since it is exactly that relativistic model that prompted my use of the idea in the thought experiment.

However, I wouldn't want anyone to get that idea that the field, and resulting forces, are in some way produced by a relativistic "effect". I make again my point that the theories only describe - they don't explain - and they certainly don't produce effects.

Sylvia.

Reply to
Sylvia Else

in article snipped-for-privacy@comcast.com, Perion at snipped-for-privacy@hotmail.com wrote on 9/28/04 12:04 PM:

Both are observing the same invariant phenomenon. Both descriptions are correct. The Lorentz transformation can be derived by modifying Newtonian theory the make both descriptions correct.

Bill

Reply to
Repeating Rifle

What I see at that URL is basically no information at all about magnetic fields.

Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

magnetic

experiment

present.

First off, electrons aren't 'stationary'. They're always moving. And then you can't 'observe' them because the act of observing them disturbs them. It's the old Heisenberg's Uncertainty Principle.

If you ask me, we're getting into the "Blind Men and the Elephant" territory.

"really"

Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

Someone named "Ken" Proclaimed on Sun, 26 Sep

2004 18:53:21 -0400,

I like this one:

A physical property of an object that shows attraction for iron, as in a magnet. Electromagnetism acts between particles with an electric charge, such as electrons, protons, and ions. It is believed to be associated with moving electricity, and it creates fields of force.

formatting link

Reply to
G. Morgan

The old "disturbance model" of quantum mechanics? That's been know to be wrong almost since the dawn of the subject.

Sylvia.

Reply to
Sylvia Else

I doubt if Maxwell's Equations can be simplified. They are elegantly simple by themselves.

However... for a layman, you may assume that anywhere there is a changing (alternating) magnetic field, in a conductive medium, their will be an associated alternating electric field that goes along with it.

There are many practical examples where these fields may be observed, calculated and measured.

  1. AC Power Lines - If you could see the magnetic lines of force, you would see a concentric circle projected from the radius of the power line increase in size as the current increases, the circle would reverse direction at the instant of maximum current flow and as the current decreases... ultimately collapsing to zero as the current goes through the zero crossing. The polarity (direction) of the circular magnetic lines of force reverses in step with the reverse of current flow in the conductor. There are simple meters that can measure both dynamic AC and static DC electromagnetic fields.

The electric field lines of force shoot our radially in all directions from an energized power line with an intensity dependant upon the voltage of the line. The electric field typically exends all the way to the ground. Insulators are designed to concentrate this voltage gradient over a fixed number of elements, thus allowing a grounded structure such as a support pylon to be brought within a few feet of the conductive cable.

  1. Radio antennas always have a magnetic field component and and an electric field associated with them.
  2. All visible light, radio, x-rays, infrared, UV energy etc. is composed of electro-magnetic radio waves of varying frequency. Air or space is considered a conductive medium in this case.

Beachcomber

Reply to
Beachcomber

magnetic

Everyone

I walked into Circuit City this afternoon and they were playing Star Wars on the big screen TVs, so I stopped and watched it for a few minutes. Luke was trying to resist Green Teeth's demand that he come over to the Dark Side; and when he didn't, old Green Teeth started zapping him with his hands. Old Darth finally couldn't take seeing his son being killed, so he threw old Green Teeth over the rail into the power reactor. And Darth ended up dying in Luke's arms.

Good special FX from Lucasfilm. I can't remember what year that was, but it's been decades since I saw that movie. And then Han finds out that Princes Leia is really Luke's sister, and they smooch and kiss, and all the little gremlins cheer them on. And they blow up the Death Star, and everyone lives happily everafter...

So what were we saying about Zone of Legality? Bubbles? Whatever happened to Bubble Memory? There's some neat magnetic fields doing some neat things. But that's now extinct.

Reply to
Watson A.Name - "Watt Sun, the Dark Remover"

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.