Author Topic: It's weird!  (Read 573 times)

Recusant

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Re: It's weird!
« Reply #15 on: June 22, 2018, 01:25:03 PM »
 
Suspending one of the bar magnets, from the light fitting and on a length of thread that places it almost exactly at the centre of the room, and placing the bar into the thread loop from either end, the end marked "N" always points North - it is therefore actually the South pole of the magnet.

Or the geomagnetic North Pole has flipped to being a South Pole without us noticing and both I and my tablet (and one of two comoasses) have been fooled . . . (I typoed "fooked" there, should have left that uncorrected!)

Same result from suspending the horseshoe magnet.

So, am I wrong in assuming, as I have done all of my life, that the end of an educational demonstration magnet marked "N" is actually that magnet's North pole - or have the Chinese fouled it up yet again?

I will pose this question in an email to "Magnet Expert", the UK sellers of the items. Let us see just how "expert" they are.

This does not cover my opposing compasses though.

Need more data! More experiments! More compasses! Need an electromagnet that I can see the winding direction on.

:lol:
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hermes2015

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Re: It's weird!
« Reply #16 on: June 22, 2018, 01:32:46 PM »
Suspending one of the bar magnets, from the light fitting and on a length of thread that places it almost exactly at the centre of the room, and placing the bar into the thread loop from either end, the end marked "N" always points North - it is therefore actually the South pole of the magnet.

Or the geomagnetic North Pole has flipped to being a South Pole without us noticing and both I and my tablet (and one of two comoasses) have been fooled . . . (I typoed "fooked" there, should have left that uncorrected!)

Same result from suspending the horseshoe magnet.

So, am I wrong in assuming, as I have done all of my life, that the end of an educational demonstration magnet marked "N" is actually that magnet's North pole - or have the Chinese fouled it up yet again?

I will pose this question in an email to "Magnet Expert", the UK sellers of the items. Let us see just how "expert" they are.

This does not cover my opposing compasses though.

Need more data! More experiments! More compasses! Need an electromagnet that I can see the winding direction on.

Have a look at this video:

Dave

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Re: It's weird!
« Reply #17 on: June 22, 2018, 02:16:13 PM »
Commendably quick response from Magnet Experts

Quote
Hello Dave,

Thank you for contacting us.

I can confirm that the North pole magnet will in fact attract to the South section on a compass. These are correctly poled as all products are produced in the same format and are Quality Checked before dispatch.

The polarities refer to North and South seeking and as N & S attract, this is why you are seeing this.

I hope this information helps Dave.

Kind Regards,


Nathan Wallace

My reply:

Quote
Thanks for your response, Nathan.

Hmm, so now the convention for educational magnets is to mark their "seeking" polarisation rather than their actual? Hmm (again), this is fine for showing that "like poles" (regardless of polarity) repel etc. Removed from all other references you could call the ends "Fred" and "Alice" and demonstrate that there is only room for one Fred (or Alice) in close proximity but that Fred and Alice share a strong mutual attraction.

But, were I introducing Hall effect devices that magnet would be "the wrong way round" would it not? The HED only knows it likes a North pole on one side or a South pole on the other, regardess of what we mark the ends of the magnet.

Basics, to me, require that the North polar end of a nagnet is marked 'N', it would make no difference to the "like/unlike poles" demo but would now agree with all other, independant, magnetic polarity and strength measuring systems. Sorry, one would still have to explain that the compass needle was "back to front" and why.

But then, who am I to question . . . ?

Dave

Am I just being pedantic or difficult that I enjoy this sort of thing? No, to my mind a thing should be marked what it is, not the opposite. And, in terms of kids learning, "Get it right first time!" Bit like religious faith and real science, teach them the wrong thing for starters and they have problems with reality later.

If the above is the current educational convention I am damn sure I will not get it changed - even if I am right in basic terms!
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Dave

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Re: It's weird!
« Reply #18 on: June 22, 2018, 02:33:01 PM »
Thanks for the video, Hermes, been using a compass to check the polarity of unmarked magnets for years. Though comparing my two current compasses . . . I have Hall effect devices and had already decided to make a polarity checker.  Which, of course, would say these educational magnets are arse-about-face from their markings.

However, already marked magnets are OK as "repel/attract" demonstrators so long as all are marked consistently. But, if the magnet in your mass spectrometer were marked as these magnets are the stream might go haring off in the wrong direction by 90o might it not? Or the motor would go backwards. Or . . .
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Dave

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Re: It's weird!
« Reply #19 on: June 22, 2018, 03:39:18 PM »
Hmm, seems the common terminology vies with the actuality. I am right from the fundamental standpoint but (as usual) at variance to the accepted practice! Pedantry strikes again.

Quote
What you have been observing is the behavior of the north and south poles of a magnet. One end of any bar magnet will always want to point north if it is freely suspended. This is called the north-seeking pole of the magnet, or simply the north pole. The opposite end is called the south pole. The needle of a compass is itself a magnet, and thus the north pole of the magnet always points north, except when it is near a strong magnet. In Experiment 1, when you bring the compass near a strong bar magnet, the needle of the compass points in the direction of the south pole of the bar magnet. When you take the compass away from the bar magnet, it again points north. So, we can conclude that the north end of a compass is attracted to the south end of a magnet.


This can be a little confusing since it would seem that what we call the North Pole of the Earth is actually its magnetically south pole. Remember that a compass is a magnet and the north pole of a magnet is attracted to the south pole of a magnet.
https://www.nde-ed.org/EducationResources/HighSchool/Magnetism/twoends.htm
(My bold)

Curiouser and curiouser . . .

But, if I had two pieces of gold foil in a vacuum bottle, each with their own connection, and the junior lab tech connected a voltage accross them they would attract each other - regardless of the polarity. But if I the junior tech marked the +ve terminal -ve  and vice versa I would not be happy when I connected my expensive, sensitive lab quality moving coil (or even electrostatic) meter to the terminals, and the meter needle took a high-speed dive backwards into the zero end stop, I would not be happy!
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Dave

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Re: It's weird!
« Reply #20 on: June 22, 2018, 06:07:28 PM »
Ok, I have been labouring all my life (well, between when I first learned of magnetic poles and until about three minutes ago) that the Earth's North Pooe was the North pole of the Earth's magentic field only to find out it is actually its South pole! Thus the "North seeking" of the bar magnets means the end pointing at the geographical top of the Earth's axis, the "Northernmost point" (ignoring the deviation), is really the actual, factual North pole of that bar megnet 'cos it points at the South pole of the Earth's field that, er, lives in the North.

Clear?

Quote
All magnets have two poles, where the lines of magnetic flux enter and emerge. By analogy with the Earth's magnetic field, these are called the magnet's "north" and "south" poles. The convention in early compasses was to call the end of the needle pointing to the Earth's North Magnetic Pole the "north pole" (or "north-seeking pole") and the other end the "south pole" (the names are often abbreviated to "N" and "S"). Because opposite poles attract, this definition means that the Earth's North Magnetic Pole is actually a magnetic south pole and the Earth's South Magnetic Pole is a magnetic north pole.
https://en.m.wikipedia.org/wiki/North_Magnetic_Pole

The magnets are correctly marked, the Earth's upper and lower ends are not. Magnetically the Earth is upside down.

The North Magnetic Pole is just a geograhical description of its location, it is the magnetic pole at the north, it's not the magnetic North pole. So the "North seeking" end of a magnet seeks geographical North, which is magnetic South.

I think that covers it.

HTF does one explain this to a 7yo? With drawings and enough time I think.
« Last Edit: June 22, 2018, 06:36:39 PM by Dave »
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hermes2015

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Re: It's weird!
« Reply #21 on: June 22, 2018, 07:08:34 PM »
Dave, you must be exhausted after all the pole dancing today.

Dave

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Re: It's weird!
« Reply #22 on: June 22, 2018, 08:01:38 PM »
Dave, you must be exhausted after all the pole dancing today.

Oh, ho, ho.

 :grin:

I was just drawn to the seeming anomaly.
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Icarus

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Re: It's weird!
« Reply #23 on: June 23, 2018, 12:50:45 AM »
Dave there are compasses that are deliberately indexed backward,  That is to say that the index mark will indicate south when the direction is actually north. Racing Dinghy sailors often use such evil devices.  The racing sailor is more interested in the directions of wind shifts or the tacking angle than he is in knowing which way he is actually going.  We are merely racing around a closed course that has buoys with which we are required to pass to our port (left) side.   Could it be that your walking stick compass is indexed in that manner?

That is not all. In various parts of the world there is magnetic deviation that is the bane of the mariners existence.  Most likely the bane of  RAF nav people too.  You would know about that of course.   Then there is the mag interference of ones house.  There are metallic objects in the floors and walls that interfere with a perfectly good compass.

Dave

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Re: It's weird!
« Reply #24 on: June 23, 2018, 03:37:11 AM »
Dave there are compasses that are deliberately indexed backward,  That is to say that the index mark will indicate south when the direction is actually north. Racing Dinghy sailors often use such evil devices.  The racing sailor is more interested in the directions of wind shifts or the tacking angle than he is in knowing which way he is actually going.  We are merely racing around a closed course that has buoys with which we are required to pass to our port (left) side.   Could it be that your walking stick compass is indexed in that manner?

That is not all. In various parts of the world there is magnetic deviation that is the bane of the mariners existence.  Most likely the bane of  RAF nav people too.  You would know about that of course.   Then there is the mag interference of ones house.  There are metallic objects in the floors and walls that interfere with a perfectly good compass.

Deviation exists everywhere (and not only magnetic), learned that in Navigation 101 in the air cadets!. Though at on line of longditude it must have the magnetic North lined up precisely with the geographical north.

As for arse-about-face-compasses; with a hiking compass you could walk off a cliff in foggy weather convinced you are wslking away from said cliff!. Gonna have to ponder that one. Not even a compass with a mirror needs a reversed needle, er, I think.
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Icarus

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Re: It's weird!
« Reply #25 on: June 24, 2018, 01:25:31 AM »
Aaah Dave you are a slave to convention   ;D   The Chinese are said to have invented the compass. One can wonder how they had it orientated.

Dave

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Re: It's weird!
« Reply #26 on: June 24, 2018, 04:03:43 AM »
Aaah Dave you are a slave to convention   ;D   The Chinese are said to have invented the compass. One can wonder how they had it orientated.

"North" and "South" are arbritsry labels. So long as the compass always points in the same directions and there is a way of deciding which of those directions is the "reference" - and good old Polaris helps there in the Northern hemisphere - then all else falls into place. So, "North/Souty", "Top/Bottom" matter not.

Neither does the fact that the North pole is actually the South pole so long as you can identify it by another mesns every time. And, once used initially, you don't need Polaris, you just identify which end of the magnetite needle pointed to it the firdt clear night you used it - or used a marked needle to draw an N-S line and used that to "calibrate" new needles.

The fascinating thing is not that they discovered the qualities of magnetite to orientate in this way but how and why? The qualities of what was to become to be called "gunpowder" were discovered, like so many things, by accident it is thought. A cook, pharmacist or alchemist allowed a mixture to boil dry then combust in a sudden flash and cloud of smoke when the pot got hot enough. Did someone just happen to hang a, maybe interesting shaped, rock up on a thread for decorative purposes and notice that it always orientated the same way?

Smoking possibly got "invented" because, in using dried leaves for making a new fire, it was noticed that breathing in for the next blow on the little fire meant breathing in some of the smoke - with interesting effects . . . We have been fools ever since!

How many discoveries have we missed because things "went wrong" and the prototype was chucked in the bin?
« Last Edit: June 24, 2018, 04:44:27 AM by Dave »
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