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It's weird!

Started by Dave, May 24, 2018, 03:50:13 AM

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Recusant

 
Quote from: Dave on June 22, 2018, 12:54:49 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:
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


hermes2015

Quote from: Dave on June 22, 2018, 12:54:49 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:
"Eventually everything connects - people, ideas, objects. The quality of the connections is the key to quality per se."
― Charles Eames

Dave

Commendably quick response from Magnet Experts

QuoteHello 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:

QuoteThanks 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!
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

Dave

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 . . .
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

Dave

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.

QuoteWhat 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!
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

Dave

#20
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?

QuoteAll 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.
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

hermes2015

Dave, you must be exhausted after all the pole dancing today.
"Eventually everything connects - people, ideas, objects. The quality of the connections is the key to quality per se."
― Charles Eames

Dave

Quote from: hermes2015 on June 22, 2018, 07:08:34 PM
Dave, you must be exhausted after all the pole dancing today.

Oh, ho, ho.

:grin:

I was just drawn to the seeming anomaly.
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

Icarus

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

Quote from: Icarus 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.

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.
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

Icarus

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

#26
Quote from: Icarus 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.

"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?
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

Dark Lightning

This all reminds me of teaching magnetostatics in high school many years ago. One of the experiments the kids did was to place a compass inside a tuna can and observe what happens. The iron shields the magnet, and when you move it around, it does not track on the earth's magnetic poles. Two of the boys had a compass that pointed E-W instead of N-S. I had no explanation except that it had possibly been demagnetized and remagnetized across the short way (which makes no sense, BTW- that small a magnetic moment wouldn't have been useful for navigation). The following summer, when going through the cabinets doing general cleanup and looking for whatever apparatus was in them that I could use, I found the cause. There was an immensely strong magnet in the cabinet below where those two were working! That magnet was so strong that if one put a steel ball on it, one could barely pull it off. I worked that into the magnetostatics lecture in the ensuing year. Lots of fun, watching the boys, all macho, trying to get the steel ball off it!

Dave

Quote from: Dark Lightning on September 22, 2018, 11:48:57 PM
This all reminds me of teaching magnetostatics in high school many years ago. One of the experiments the kids did was to place a compass inside a tuna can and observe what happens. The iron shields the magnet, and when you move it around, it does not track on the earth's magnetic poles. Two of the boys had a compass that pointed E-W instead of N-S. I had no explanation except that it had possibly been demagnetized and remagnetized across the short way (which makes no sense, BTW- that small a magnetic moment wouldn't have been useful for navigation). The following summer, when going through the cabinets doing general cleanup and looking for whatever apparatus was in them that I could use, I found the cause. There was an immensely strong magnet in the cabinet below where those two were working! That magnet was so strong that if one put a steel ball on it, one could barely pull it off. I worked that into the magnetostatics lecture in the ensuing year. Lots of fun, watching the boys, all macho, trying to get the steel ball off it!

Good story, DL.

I am passing some magets onto to a nrighbour's grandson - better he picks up some knowledge from playing with them rather than they lay aroundnin my drawers and boxes of stuff. At 7yo he is heavily into Leggo so perhaps a budding engineer or scientist. He only gets the weaker and spherical ones, plus a horseshoe, 'cos the powerful rectangular neodymium ones hurt me if I get skin caught between them!

I thought about a compass, I had a never-used trekking compass somewhere and dug it out. The needle was half painted with  "luminous" paint and I assumed that was the north seeking end. Uh-uh, it was the south seeking one, the "blued" end pointed north.

It was during this period that I discovered, much to my surprise that it had not been taught or occured to me as a kid, that the Earth's North Pole is actually a magnetic south pole!

Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74

Dave

I have a "Brooke's Light Mill", aka radiometer, thst I bought about 15 years ago. Entropy rules so, eventually, even the hard needle bearing and the glass cup that rests on it wears a bit, increasing "stiction" and all through the very sunny summer it would not work without a tap.

Now, in the cooler almost fall sun, it trundles quite happily at any half decent bit of shiny stuff. The only thing I can think of is that the high, dummer, dun hits its vanes st an rather acute angle. Looking at the shadows at the moment the light angle is just about 45o.

Do I need to make a black body and use my IR thermometer to measure its temperature and get the big protractor from upstairs to measure the angle. Maybe a laser/detector to attach to my 'scope to count the rotational frequency of the vanes, taking readings every hour . . .

Oh, maybe when I feel better (if it is still sunny then).
Tomorrow is precious, don't ruin it by fouling up today.
Passed Monday 10th Dec 2018 age 74