Magnetic field on earth?

[Rafiqul Islam]

I am a student of science.

I know that the compus works for magnetic field on earth.But I don't know the actual cause of this magnetic field.Compus always set in north and south direction. Sometime I thing ,Is there any magnetic hill on north or south poll?Or this is the cause of spin of the earth.

 

But what is right description of this magnetic field?

Edited May 29, 2015 by Rafiqul Islam

[ajb]

The basic mechanism is that the outer core of the earth consists of liquid iron and the flow of this liquid generates electric currents which in turn generate magnetic fields. The Coriolis force helps to roughly align the magnetic fields generated and so we have net magnetic field.

Edited May 29, 2015 by ajb

[Sensei]

Compus always set in north and south direction.

Not always compass shows Earth's magnetic field.

When there is present permanent magnet, electromagnet, or wire through which there is flowing current, compass will show "wrong" direction.

 

If you're really interested in magnetic field, you should buy compass array device.

It'll visualize magnetic field lines:

 

It's made of hundred compasses packed together.

 

[eswit12344]

Earth is a large mass and in return it has effects on gravity just like a ball on a net a net of gravity time and space.

[Strange]

Earth is a large mass and in return it has effects on gravity just like a ball on a net a net of gravity time and space.

 

That doesn't have anything to do with the magnetic field, though.

[Enthalpy]

Hey, if you invent a compass that points to Mecca insterad of North, you're rich!

OK, OK, joke besides.

 

The cause of the geomagnetic field is so little simple that it was debated few years ago. After all, a piece of copper or iron doesn't produce a magnetic field just because it rotates. An experiment with liquid sodium has settled the debate more or less

http://perso.ens-lyon.fr/nicolas.plihon/VKS/index.php

Though, the necessity of a liquid core and a few hours rotation doesn't always fit easily with what we observe from other planets.

 

From what I believe (or not) to have grasped:

• The hot Earth core creates convection, at several places.
• Iron (conductive, not magnetic at that temperature) traps some pre-existing magnetic flux, just because it's a big chunk where currents take typically 10,000 years to dampen out, that is, the inductance increases with the size but the resistance drops.
• That's the typical timescale of variations in the geomagnetic field. Several convection chimeys result in a global field that is tilted, excentered, variable and reversible over time.
• Earth's rotation messes somehow in.
• As metal ascends in convection and grasps speed, it gets narrower and longer, but the trapped flux being concentrated increases the induction.
• Non-trivial: the narrower but longer metal creates at some identical distance a stronger induction. R/2 and flux*1 implies B*4 over h*4, resulting from I*16, so I*S gets *4 and this is what determines the remote induction.
• The ascending chunk of metal can create an induction stronger than the one it experienced before ascending, so the field may amplify and perpetuate.

Please take with much mistrust..