Re: [Phys-l] Good Questions

[Brian Whatcott <betwys1@sbcglobal.net>]

At 01:35 PM 10/10/2006, Jeff Schnick, you wrote:
///
> 2) (A psychology professor [...who] was doing Alzheimer research on rats
> using the Morris water maze
> http://www.watermaze.org/
> asked me about this one.)  How would you go about canceling out the
> earth's magnetic field in the region of the surface of the water in a
> 1-meter deep pool (he used a deeper pool than the one depicted at
> watermaze.org) of water having a circular surface of diameter 1.8
> meters?


I was bemused by this particular question. Anyone who was
contemplating bio-magnetic effects would surely be familiar
with the standard device for neutralizing the Geomagnetic field
 - namely Helmholtz coils.

Because the greatest field homogeneity is reached only in the
central region, there is possibly a concern that a pair of
 coils needed to handle the appreciable volume in question
 might be taller than one could easily accommodate.

I recall being shown an experimental rig consisting of coils
 wound on bike rims (at Clarendon Lab) which is to say - coils
 do not need to be entirely air spaced, nor round, nor yet
 limited to twins.


Brian Whatcott    Altus OK    Eureka!