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Magnet attraction and repulsion...

Posted: Mon Oct 13, 2008 8:39 am
Hi all.

A couple of square iron bars, say 1/4" , say 20" long, say spaced a couple of inches.

A magnet (M) across the left end :

N=========================
M
S=========================

Should at the right end of the bars appear the same N, S polarity ?

If so, placing another magnet at the right end in the same orientation as the one at the left end (N on top, S down) would be repelled by the right end of the bars.

Well, it does not. It sticks to the bars in any orientation. Why?

Miguel

Re: Magnet attraction and repulsion...

Posted: Mon Oct 13, 2008 12:06 pm
Externet wrote:Hi all.

A couple of square iron bars, say 1/4" , say 20" long, say spaced a couple of inches.

A magnet (M) across the left end :

N=========================
M
S=========================

Should at the right end of the bars appear the same N, S polarity ?
You have not accounted for the flux leakage between
the poles along the length of the rods.

Try placing a sheet of paper over the magnet and
rods and sprinkling iron filings. If you gently tap
the paper the iron filings will align with the flux
lines. Most of the magnetic attraction will be near
the magnet, weakening towards the far end of
the rods.

Place the second magnet in "poles opposing" to the
first one at the open end of the rods. You should
see a null halfway down the rods as the two magnet's
fields cancels.

What are you trying to achieve?

Posted: Mon Oct 13, 2008 12:13 pm
Hi Miguel,

A north pole always seeks a south pole, and vice versa.
This means magnets placed pole to pole (notice i did not
say 'end to end') will always stick together such that
N goes to S and S goes to N. That's the way it is, period.

If this is not working for you, then there is either something
wrong with the way the poles orientations are being assumed,
or else one of the magnets is weaker than the other and
is acting like a piece of metal rather than a magnet.

Be aware that some magnets that are long have poles
that are not at the ends, but rather on two opposite sides.
It all depends on what direction they were facing when
magnetized.

Re: Magnet attraction and repulsion...

Posted: Mon Oct 13, 2008 1:13 pm
[quote="BigglezYou have not accounted for the flux leakage between
the poles along the length of the rods.

What are you trying to achieve?[/quote]

OK, the bars are supposed to act like a stretched horseshoe type magnet, where the poles appear near the tips. But not much action there.

There could be some 'losses' per distance which I have seen in books for free space yes, but inside a magnetic material, nope.

And the poles from (M) should have moved to one tenth the lenght of the right tips by the assembly. Does not seem like. (distance between centers of pole zones = 4/5 lenght of magnet)

Trying to achieve? Really nothing, trying to make a toy for a kid, a section of magnetic 'railroad' and a repelled car floating on it.
I have too many lazy rare earth magnets that could teach (or amaze) a kid...

Miguel

Posted: Mon Oct 13, 2008 2:56 pm
Hi again,

Miguel, did you test all the magnets to make sure the poles
orientations were exactly the way you think they were?
What about the strength of the smaller magnet?

Posted: Mon Oct 13, 2008 4:00 pm
Speaking of magnets and north and south poles, I just read that a compass is useless for finding your way on Mars as Mars has no magnetic field. So much for assumptions that I've had about planets! The Mars Sojourner had to get a fix on the sun and know the precise time of the Martian day in order to know where "north" was.

Dean

Posted: Mon Oct 13, 2008 6:11 pm
Hello Al.
The 2 magnets are identical, poles marked with a compass as reference; rods are identical from the hardware store; and no matter how they are oriented respect to each other, they stick to the rods. Sliding them closer together to any position along the rods behaves the same!

N====================N
S====================S

====N==N==============
====S==S==============

My daughter borrowed my camera and will not have it back for a few days, just visualize a perfectly placed symmetric array.

One of dozens of related sites:
http://www.coolmagnetman.com/magtrain.htm

Miguel

Posted: Tue Oct 14, 2008 2:36 am
Hi again,

Dean:
That's not surprising as Mars is on the list of worst vacation
spots

Miguel:
I have several magnets all the same exact shape and strength,
and they all stick together N to S and S to N, and that's it.

Posted: Tue Oct 14, 2008 5:59 am
By definition the North pole of a magnet will be attracted to the Earth's North pole. This so confused me in grade school science! Seems like they should change one or the other
Dave

Posted: Tue Oct 14, 2008 6:06 am
Hi,

According to research the earths poles will be changing again,
so eventually N will become S and vice versa. All current
compasses will be backwards.

Posted: Tue Oct 14, 2008 6:11 am
Dave Dixon wrote: Seems like they should change one or the other
Dave
They did.
Now it is renamed to "North seeking pole"

Miguel