Is the North Pole a south pole?

[UKpete]

I'm confused - I have a Martindale TEK200 Magnetic Indicator and the instruction manual that accompanies it states on page 5:

"Note: also that a compass needle is a North Pole. It is attracted to point towards the south pole of any other magnet and NOT the north pole of any other magnet."

http://www.martindale-electric.co.uk/instructions/TEK

200 instruct rev 1.pdf

And when I use the TEK200 to identify the south pole of a magnet (taking care to use it correctly as defined by their manual), my pocket compass points to the same magnet pole as though it is the earth's north pole.

Is this correct? I always assumed that a compass needle would point towards the north pole of a magnet.

 

[MJR2]

If the compass needle is a magnet. It would have north and south poles. The north pole would be atracted towards the earth's south pole. Therefore paint the needle's south pole to indicate pointing north.

 

[IRstuff]

see:

http://www.answers.com/topic/north-pole

A magnet has a north (seeking) pole. Likewise a compass. Therefore, a compass' north pointing end would attracted to another magnet's south pole.

TTFN

 

[UKpete]

Ok, so if you sneak the word "seeking" into the description of any magnet pole it all fits. So the compass needle (itself a north [seeking] pole) points to the south [seeking] pole of another magnet because unlike poles attract.

I don't suppose I'm the first or the last to get caught out by that one.

 

[MagMike]

Hello UKpete,

For the definition of the North Pole, I always fall back on the one published by the IMA (formerly MMPA):
"The North pole of a magnet is that pole which is attracted to the geographic North pole. Therefore, the North pole of a magnet will repel the north seeking pole of a compass"

There is that extra term "seeking"...

You are definitely not the first nor last to go through this. I get about one call per month on just this question.

 

[electricpete]

So if the earth were a giant magnet and we were to evaluate it's polarity, the magnetic north pole lies at the place we call the geographic south pole?

Who came up with that crazy system?

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[electricpete]

I did notice in IR Stuff's link where it says the flux above the north pole has a direction straight down into the ground (and flux above south pole would be straight up out of the ground).

Using what we learned in physics, flux travels N->S outside of a manget (and S->N inside). Looking at the region outside the earth/magnet, it is consistent with N geogrphic pole acting like south magnetic pole.

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[IRstuff]

I think you're getting too hung up on the "polarity." It's all be convention anyway.

The only other choice would have been to make magnet south poles point north, which I don't see to be an improvement. It's a binary problem and the current conventions make it easier for most people to deal with magnets.

TTFN

 

[UKpete]

If you compare the earth to a magnet, at (or near) the geographic north pole is in fact a south [seeking] magnetic pole, in magnet terms abbreviated to a south pole.

To be fair to the pioneers, it probably took a while to catch on to the fact that unlike poles attract. Like the direction of conventional current in a circuit (as opposed to electron current being in the opposite direction, as discovered later) the original definition has been left unaltered.

 

[electricpete]

IRStuff – I think you are too hung up on conventions.

Anyone working with magnets will have to know that opposite poles attract. Therefore there would be every reason to suspect that the end of the needle of a compass which points to the north pole of any magnet is a south magnetic pole of the needle. In fact that is the case when we work with permanent magnets.

But we have reversed this convention when it comes to treating the earth as a magnet because apparently some people think that directions should be identified by magnetic polarity of the compass needle and not by magnetic polarity of the earth. This makes no sense to me because when I look at a compass I am interested in judging the magnetic polarity of the flux that is being measured, and not interested in the magnetic polarity of the needle.

It is not analogous to the current convention. Current convention does not depend on the circuit. The magnetic north/south convention selected does depend on the magnet we select. It is different if we select the earth as a magnet than if we select any other permanent magnet.

UKPete – “south [seeking] magnetic pole” is an ambiguous term to me because south magnetic pole is different than south [seeking] magnetic pole. I would say the geographic north pole of the earth is a magnetic south pole but it is not a south-seeking magnetic pole.

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[IRstuff]

How can I be hung up on conventions if I don't think it makes any difference?

But for 99.9% of the people in the world, all they care about magnets is that they can find the earth's magnetic north pole. And for that, they want the end of the magnet that points north to be labelled "north."

TTFN

 

[UKpete]

EPete, the electric circuit current convention isn't a direct analogy of the magnetic pole situation. What I meant was that in the same way as with the current convention, the pioneers got it wrong but we still live with it.

It is conceivable that it all came about because in the early days it was thought that like poles attracted (or indeed that that magnetism was unipolar, in the same way as gravity). There was no independent method of proving it was otherwise (such as by the Hall effect or by galvanometer) and compass needle magnets weren't strong enough to repel each other, or it just wasn't noticed. I don't know; but at least I know now that a compass points to the south pole of a magnet, I won't make that mistake again!

 

[electricpete]

"But for 99.9% of the people in the world, all they care about magnets is that they can find the earth's magnetic north pole."

It might not be standard useage but when you use the words "earth's magnetic north pole" given the above discussion I conclude you are talking about the magnetic pole nearest the geographic south pole. That is the pole of the earth that is a magnetic north pole.

"And for that, they want the end of the magnet that points north to be labelled north."

I agree the compass needle needs to be labeled the same as the direction it points. So we have two choices, mislabel the polarity of the compass needle magnet, or mislabel the polarity of the earth magnet. We chose to mislabel the earth which creates the ridiculous terminology discussed above. I would have chosen to mislabel the magnet on the compass needle and keep the earth correct.

Scotty - you are probably right about the way this evolved. Anyway I definitely learned something brand new in this thread about the poles. Good thread.

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[IRstuff]

Actually, I was refering to the pole that's geographically north.

And you point the fundamental flaw in "correct." There is no "correct". The north pole is ONLY signficant because the mapmakers of yore all lived north of the equator. And, it's only significant because of when this discussion is taking place.

If you a few hundred thousand years, you'll get your wish, since we're a bit overdue for pole flipping:

http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm

TTFN

 

[UKpete]

IRstuff, I also think it's a bit unfortunate that southern hemispherians are considered to be on the bottom of the earth. So to be politically correct I always flip our globe over on it's stand when we are expecting any Australian visitors. Come to think of it, we don't get many visitors.

 

[IRstuff]

He who draws the first map gets the globe oriented his way.

What REALLY galls me is getting a restaurant ad with a nice little map oriented with north-south running left-right

TTFN

 

[lemwells]

When compasses were invented, the direction of flux travel inot and out of their respective poles was unknown, not even imagined. Which end of the needle was called North was simply a matter of naming it.

Fast forward many years.

Physisists decided that magnetic flux travels from positive to negative (like they thought electricity did) and decided that North should be positive. Apparently, these guys weren't Australians either.

Anyway, that leaves us with the fact that flux travels toward the geographic North pole making it a MAGNETIC South pole.

Once time travel is perfected, we can go back and tell the idiot that picked it wrong all those centuries ago to get it right. Until then we should just take comfort in the fact that magnet needle always point the same way and label it according to geography. We should also leave geography out of instruction manuals for flux meters and the like.

There's a little of my usless knowledge AND a couple of opinions. No charge.

 

[Warpspeed]

Anyhow mate, when I look out of my Australian window at the sun, or the moon, it is always south pole upwards.

What idiot decided that north should be shown at the top of the map ? It is bloody hard reading a map when all the place names are upside down.

 

[IRstuff]

Actually, those would have be your ancestors ;-)

TTFN

 

[electricpete]

Mates - In Australia, July/August would be cold season. Do they call it winter or summmer?

(It's a real question, not a joke. I'm just curious).

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