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Up Topic Chit-Chat & Non-Welding Discussion / Off-Topic Bar and Grill / Magnetics
- - By Mikeqc1 (****) Date 04-28-2011 20:09
Please chime in on this…….
The earth has a magnetic field, like a bar magnet. The line of force exits out of the north pole and enters at the south, and “flowing” south to north on the inside.
A  ring magnetized longitudinally has no north or south pole and therefore has no external field.
How does a  Sphere behave when magnetized?
Is there a North and South pole and what determines the position if they are created?
Parent - By jwright650 (*****) Date 04-28-2011 20:16
Same topic but off course just a little because I thought it was fascinating....

check out this: Earth
Parent - - By jwright650 (*****) Date 04-28-2011 20:22
The individual domains that are made up of tiny N/S poles will determine where the N/S poles are......
Parent - - By Mikeqc1 (****) Date 04-28-2011 20:45
Right ...but will say a ball bearing have an external field.

A ring will not, will a sphere
Parent - By jwright650 (*****) Date 04-28-2011 20:47
It depends on which way the domains where aligned when the sphere was formed.
Parent - - By rlitman (***) Date 04-29-2011 19:06
A ring will.
You're thinking of a "field" as a single vector value.
A "field" is like the wind.  It may be northerly where you're standing, but around the globe, the wind goes in all sorts of directions.
In your ring example, if the magnetic domains are aligned longitudinally, there is no net field at the axis of the ring, but anywhere else, the field will be aligned parallel to the circumference of the ring (with a maximum flux on the surface of the ring.)

You certainly can magnetize a sphere, by aligning the magnetic domains parallel to a particular diameter.  It will still behave like a bar magnet, except with a "rounder" surface.
Parent - By Mikeqc1 (****) Date 04-29-2011 19:27
If a bar magnet is fused into a ring the magnetic circuit is fully contained within the circuit and No external field exists.
Parent - By Mikeqc1 (****) Date 04-29-2011 21:32
If a Sphere is of a material that can be magnetized you can set up the internal field no doubt, my question is would there be a north and south pole(I know the earth does). I wonder if a longitudinal or circular field makes a difference. Like if  you do a direct head shot or indirect coil.
the curie point is about 800 deg f (don’t have ref mat) for most metals, where the material becomes diamagnetic, if that holds true for molten rock and the Material was aligned magnetically when in hot liquid form couldn’t that mean the poles of the earth at that time were 90 deg to the direction of the field in the samples?
Parent - - By 357max (***) Date 04-28-2011 22:51
So lets be practical; what direction should pipe be laid in the yard to minimize the magnetizing and creation of magnetic arc blow?
Parent - - By Superflux (****) Date 04-29-2011 06:54
Aligned to Magnetic North for a controlled magnetizing???
Parent - By jwright650 (*****) Date 04-29-2011 12:52
I think that is what happens when the material is molten....the domains are free to move and align...in old lava flows they can determine where mag North was at the time the lava was cooling(freezes the domains in a position) by examining the domains and how they are aligned.
Parent - - By Mikeqc1 (****) Date 04-29-2011 21:38
I was told ships and subs can become magnitized when on long trips because the water flows in the same direction for a long time.I thought there was a rule that ships are built or launched in a certain direction to avoid a field /or demagnatize it.
Parent - By bozaktwo1 (***) Date 04-30-2011 01:08 Edited 04-30-2011 01:12
Ships and submarines are made of large amounts of iron.  As they move about the earth, they do indeed acquire a magnetic "signature" and this is usually countered with a thorough degaussing.  However, it makes no difference which way a ship is launched.

EDIT: There are many phenomena involving the earth's magnetic field, the most famous of which is the aurora borealis. Those who have traveled in ships with cathode ray tube-style televisions can attest that the picture is decidedly undecipherable after 13000 miles or so.
Parent - By CWI555 (*****) Date 05-01-2011 21:48
Pipe should be laid east west if you expect to weld on it.
Parent - - By Cactusthewelder (*****) Date 04-29-2011 12:20
Send a Message to KFAB. He is on here. He is heavily involved in the study of magnets when placed into a Sphere. It will amaze you to listen to what he does with these things
Parent - - By Mikeqc1 (****) Date 04-29-2011 15:58
in the hand book for NDE (Charles Hellier)
i read the following.....if a magnetic rod were hung in the middle it will eventually align itself with  the earth mag field so that 1 end points to Geographic north and the other end south.If the north pointing end is identified it will be found this end always points north  this end of the rod is called the NORTH SEEKING pole or NORTH POLE for short.
...based on that wouldnt the north pole (of earth) in this case actualy be the south pole?
Or is what is in this book wrong?
Parent - - By Superflux (****) Date 04-29-2011 17:05 Edited 04-29-2011 17:10
"if a magnetic rod were hung in the middle it will eventually align itself with the earth mag field so that 1 end points to Geographic north"

1) Well, I think this type device is called a COMPASS.
2) The editor of the book is wrong. A magnetic rod free hanging (a compass) will point to MAGNETIC NORTH.

Magnetic North can be several degrees off geographic North, depending on your location. Stellar north (the North Star) is up to one degree off the rotational axis of the planet...depending on the time and season.
Parent - By Mikeqc1 (****) Date 04-29-2011 19:00
yes but the north pole swings south................
Parent - - By CWI555 (*****) Date 05-01-2011 22:21
Mike,

talking about the earths magnetic field vs a simple bar magnet is like comparing a ballistic missile vs an arrow.

However; if you wish to perform some simple experiments, buy a rare earth magnet in the shape of a sphere.
There is a lot of data that has come out in the last few years regarding the field of magnetics. One of those things is confirmation of the existence of magnetic monopoles.
http://www.popsci.com/technology/article/2009-10/newly-dicovered-monopole-particles-flow-electric-currents


In regards to the mentioned magnetic lines in the earth:

It's to be noted that the magnetic domains recorded in the Atlantic ridge cores did not align until they got below the curie point.

To add confusion to the problem it has also been discovered that the earth is constantly being bombarded via flux ropes from the sun.

http://en.wikipedia.org/wiki/THEMIS

There are some who are starting to believe part of the process that keeps the earths core hot, is the combining of monopoles into dipole domains, and that in fact, the flux ropes connecting the earth to the sun are the source of those monopoles.

Simply put, there is no comparison between the earth and a simple sphere magnet formed by normal means.

A neodymium magnet when formed in a sphere will align it's domains with the direction in which it was energized initially. It is simply a function of the magnetic domains.
Parent - - By Mikeqc1 (****) Date 07-13-2011 23:10
there is a error in the ASNT LVL III sudy material, the book states that the curie point makes the steel become diamegnetic, and i have since learned it becomes paramagnetic.......look out when using ASNT study material its full of errors.
MDK
Just passed my MT LVL III...Im sure that ASNT not only wishes to test the canidate in the method of NDE , but also our power of ESP.......the questions where........ODD.
Parent - - By CWI555 (*****) Date 07-14-2011 15:56
Congrats on passing the test.
Parent - By Mikeqc1 (****) Date 07-14-2011 19:05
thanks.
Up Topic Chit-Chat & Non-Welding Discussion / Off-Topic Bar and Grill / Magnetics

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