Help with terrestrial magnetism

[sachin123]

I have a bunch of conceptual questions on Earth's magnetism.
The problem is I have not understood the elements there.
I am not able to visualize the magnetic field ,horizontal component,declination,inclination.
I don't know the directions of them too.
My book hasn't given pictures of them either.I am finding this really hard.
Can someone link a good tutorial or something for this?Or a good book with pictures?
I hope it was not wrong to ask.
Thanks

 

[sachin123]

Does vertical here mean,our vertical?I mean for people on the ground?(to the sky?)

 

[gomunkul51]

http://en.wikipedia.org/wiki/Earth's_magnetic_field

 

[sachin123]

It doesn't give pictures or any thing.How have the others understood this?Books?
I didn't attend this in college.

 

[gneill]

http://www.google.ca/images?hl=en&q...cOXtwfwwNiUDA&ved=0CDcQsAQ&biw=1156&bih=1104" you're happy with.

 

[sachin123]

Hey,are the geographic north and magnetic north in the same hemisphere?
My book says otherwise,but this image:http://www.google.ca/imgres?imgurl=http://www.teara.govt.nz/files/di7245enz.jpg&imgrefurl=http://www.teara.govt.nz/en/bird-migration/6/4&usg=__7lTwRYXV6ifmlxNUUnvtzIO63ig=&h=530&w=498&sz=34&hl=en&start=13&zoom=1&tbnid=sNE2OPsJw_q_GM:&tbnh=146&tbnw=137&ei=GthfTejvA4OovQOLhuSHAg&prev=/images%3Fq%3Dmagnetic%2Bfield%2Bof%2Bearth%26um%3D1%26hl%3Den%26sa%3DX%26biw%3D1054%26bih%3D616%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=128&vpy=95&dur=1020&hovh=232&hovw=218&tx=130&ty=115&oei=oddfTYGGFdDRrQfd_7y8AQ&page=2&ndsp=15&ved=1t:429,r:0,s:13
And none of the images show elements of magnetism.:(

 

[gneill]

By geographic convention, "magnetic north" is the direction to the location in the northern hemisphere where the angle the magnetic field lines make with the surface of the Earth is 90 degrees (the field lines are vertical there). Also we call that location the North Magnetic Pole.

It should be noted that our convention for how to assign magnetic poles to magnets came from the fact that one "end" of a magnet was attracted to the direction of the north magnetic pole, and we called that end the "north pole" of the magnet. What this means, of course, is that the Magnetic North Pole is actually the location above the Earth magnet's south pole. Similarly, the Magnetic South Pole (in the Antarctic) is actually the location above the Earth magnet's north pole.

The naming convention for the Earth's magnetic poles is more Geographical than Physical.

 

[sachin123]

hi gneill.Sorry,but I didn't understand what you mean.
What do you mean:
the location """"above"""" the Earth
?
And I thought the north pole of magnet was attracted to south pole of Earth.Thats how it is supposed to be right?

So basically,referring to the world maps on globes(only geographical),
the geographic north and magnetic north are in the same hemisphere right?
Can you comment on the image I linked?(right click and copy link if you can't see it)

AND what do you mean
the naming convention for the Earth's magnetic poles is """more"""" Geographical than Physical?
the physical names are given referring to the geographical ones?

And one more:
if i suspend a bar magnet in free air,
will it tilt down a little(us looking at it,like it is a slide)?Is this what is referred to as dip?

Thanks

 

[gneill]

hi gneill.Sorry,but I didn't understand what you mean.
What do you mean:
the location """"above"""" the Earth

Imagine that there is a large bar magnet buried inside the Earth. Above a pole of that bar magnet the field is vertically directed to the local horizontal. That is, the field lines make an angle of 90 degrees to the ground there. So "above" the Earth's surface...

?
And I thought the north pole of magnet was attracted to south pole of Earth.Thats how it is supposed to be right?

It might be nice if it were so, but no. As I stated, the convention came from naming the end of a magnet that was attracted in the direction of the north pole of the Earth the "north pole" of that magnet. Again, if you were to imagine a giant bar magnet inside the Earth, then that bar magnet's north pole would be near the south geographic pole of the Earth, and its south pole would be near the north geographic pole.

See the second figure on http://en.wikipedia.org/wiki/Earth%27s_magnetic_field" .

So basically,referring to the world maps on globes(only geographical),
the geographic north and magnetic north are in the same hemisphere right?
Can you comment on the image I linked?(right click and copy link if you can't see it)

AND what do you mean
the naming convention for the Earth's magnetic poles is """more"""" Geographical than Physical?
the physical names are given referring to the geographical ones?

Yes. The term "magnetic north" refers to the direction of where the magnetic pole is in the north. But the north magnetic pole is really a south pole of the Earth's magnetic field.

As I have stated before, the naming convention for magnets is due to the direction they pointed (geographical).

And one more:
if i suspend a bar magnet in free air,
will it tilt down a little(us looking at it,like it is a slide)?Is this what is referred to as dip?
Thanks

Yes. And dip at the poles is 90 degrees.

 

[sachin123]

So from what I understood from your posts is that,if we were to assume a magnet in the Earth,its N pole would be near Antarctica and S near the Arctic.
But the naming is done the other way round.
So are there 2 terms "magnetic north" and "magnetic north pole"?
Which of them is usually referred to?

And,about horizontal component of Earths magnetic field,like had I asked then,...
when the magnet is suspended,the component of magnetic field in the horizontal(like a flat golf course)is what horizontal component of Earths magnetic field is?Its just like a body falling down at an angle.you can resolve the velocity into "HORIZONTAL" and vertical components.RIght?

And one more,in a question,a coil is placed vertically (like a tower is)and a person facing North,looks a it and finds the current in the coil in clockwise direction.So,what North is being referred to now?

And one more,what countries to magnetic north and south correspond to?

 

[gneill]

So from what I understood from your posts is that,if we were to assume a magnet in the Earth,its N pole would be near Antarctica and S near the Arctic.
But the naming is done the other way round.
So are there 2 terms "magnetic north" and "magnetic north pole"?
Which of them is usually referred to?

"Magnetic north" is the direction to the "magnetic north pole". Either is used where appropriate, depending upon what it is you're trying to say.

And,about horizontal component of Earths magnetic field,like had I asked then,...
when the magnet is suspended,the component of magnetic field in the horizontal(like a flat golf course)is what horizontal component of Earths magnetic field is?Its just like a body falling down at an angle.you can resolve the velocity into "HORIZONTAL" and vertical components.RIght?

Sure. At any point along a given field line you can construct a vector that points in the direction of the field at that point. That vector will have components in whatever frame of reference (coordinate system) you are using.

And one more,in a question,a coil is placed vertically (like a tower is)and a person facing North,looks a it and finds the current in the coil in clockwise direction.So,what North is being referred to now?

I don't understand. It's your question, so *you* have to specify whether he's facing the north pole of a magnet or the north pole of the Earth.

And one more,what countries to magnetic north and south correspond to?

Canada and the antarctic currently, although strictly speaking Antarctica is a continent, not a country. There are no countries in Antarctica.

 

[sachin123]

So magnetic north is the DIRECTION from the point"magnetic south pole"to the "magnetic north pole"of that imaginary magnet?
In that case you must have meant 'antarctic and the Canada currently' and not
'Canada and the antarctic' currently right?Places can refer to points and poles but not directions.Correct?

About the question,thats all they have mentioned.Lets leave out the geographic poles and consider only magnetic,can there still be a doubt on whether they referred to poles or directions?

 

[sachin123]

Looking at the solutions for the question,I have found that they refer to looking in the direction of magnetic north (ie,towards the imaginary south pole) so that the field due to current in the coil adds up to the Earth's magnetic field(which is from towards the north direction,from N pole to S pole).
Was that obvious?

 

[gneill]

So magnetic north is the DIRECTION from the point"magnetic south pole"to the "magnetic north pole"of that imaginary magnet?
In that case you must have meant 'antarctic and the Canada currently' and not
'Canada and the antarctic' currently right?Places can refer to points and poles but not directions.Correct?

No. Magnetic north (direction) is the direction to the north magnetic pole (place) which is where the south pole of an imaginary bar magnet creating the Earth's magnetic field lies buried. You do not have to be at the magnetic south pole to define this direction. You can point to the magnetic north pole from any location on Earth, and that is magnetic north for that location.

Magnetic north is the direction of the north magnetic pole which is currently located in Canada.

About the question,thats all they have mentioned.Lets leave out the geographic poles and consider only magnetic,can there still be a doubt on whether they referred to poles or directions?

You're worrying and nit-picking over word semantic issues that can occur when we mix magnets and geography and the magnetic field of the Earth. I can't be bothered playing that game any more. I've done my best to explain. Further information can be found in numerous reference works available via the web.

Just understand that magnets have poles. The Earth has a magnetic field. The field of the Earth is like a giant bar magnet with its south pole near the geographic north pole, and its north pole near the geographic south pole. When talking geographically, magnetic north refers to the direction of the geographically northern pole. When talking about a magnet we refer to the north and south poles of the magnet. A properly worded problem statement should make it clear by either context or specific detail what is being referred to in each case.

 

[sachin123]

Okay,I get it(they are like any directions),
I meant to ask:
So magnetic north is the DIRECTION from the point"magnetic north pole"to the "magnetic south pole"of that imaginary magnet?

Sorry there.
And thanks a lot really