Re: Earth's magnetic field

[brian whatcott <inet@intellisys.net>]

At 18:47 10/25/97 +0000, Inge wrote:
> I am sorry for this late answer, but here we go:
> In my high school students measure the magnitude of
> the horizontal component of the earths magnetic field 
> by the following procedure:
> 1. Place a compass inside a coil with the coil pointing
>   in the east-west direction (no current !)
> 2. Apply a small current (with our apparatus 70 mA) to
>   the coil so that the compass needle is making 45 
>   degrees with the north-south direction. The horizontal
>   geomagnetic force should then be equal to the magnetic
>   force from the coil.
> Typical values we get are 3*10^(-5) T, which is not bad
> according to tabulated values.


I'm so pleased you mentioned your experimental determination.
For some reason the figure of 470 microtesla for total field
comes to mind  which contrasts strongly with your value of 
30 microtesla for horiz. component.

 I can't think that your latitude is so Northerly as to make 
the vertical component of the field so predominant - so my 
remembrance is probably faulty.
 But if you have a dip needle you could repeat the experiment 
for the vertical component - or do you already run this measure?

 I fancy people on this list were reticent as to values possibly 
because there is the academic preoccupation with appropriate units 
- Tesla vs. Amperes per meter, B vs H etc...

Sincerely,

brian whatcott <inet@intellisys.net>
Altus OK