# Magnetic field lines of earth

1. Apr 3, 2014

### College3214

I need help understanding a certain problem. It basically stated: an airplane accumulated a positive charge, heading westward above the equator. Find the direction of the force (using the lame right hand rule thing).

The problem I had was figuring out was whether the magnetic field would hit the plane at the top or bottom. I know the magnetic field lines go from earths's south geographic to north geographic poles. My answer was that the force would be outwards from the plane of the paper, but the correct answer was inwards. The trouble I had was visualizing earth as a magnet. I know no field lines go through a magnet, so if the fields originate at the poles, in what direction do they go when it's something above the equator...do they circle the earth and then dip back down towards the south geographies pole, or go directly from the south to north geographies poles?

2. Apr 3, 2014

3. Apr 3, 2014

### rude man

Along the equator the B field points roughly horizontal and North.
Then figure out q v x B direction.

4. Apr 3, 2014

### lightgrav

Welcome to PF!
Magnetic Field lines DO go thru the magnet ... they are most intense within the magnetic material.
(this is inverse of Electric Fields thru dielectric).
Magnetic Fields do NOT start at one pole and end at the other (like E-fields do from +Q to -Q),
they exit N pole region and enter S pole region, but they do not END there.
adjascent's drawing shows 5 lines northward outside Earth
(the outermost should be farther out, with larger spacing to show less intensity)
there need to be 5 lines inside Earth also, from N (where they enter) to S (where they exit).

B never diverges anywhere, which means that there is no scalar that can be a source for B.
... rather, B is produced by vectors (Qv, I, μ) or induced by changing vectors (Qa, ΔI/Δt, ΔE/Δt)