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From: John Larkin on 3 Mar 2010 15:21
On Wed, 3 Mar 2010 10:36:42 -0800, dplatt(a)radagast.org (Dave Platt)
wrote:

>In article <2ktso5pli2bs2n0kvetfnp4psps4ib9qv0(a)4ax.com>,
>John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>
>>Is there such a thing as a spherical magnetic field? Where would all
>>the vectors point?
>
>It could be done with isolated magnetic monopoles, I suppose.
>Unfortunately, they seem to be out of stock at all of the popular
>suppliers, and I have my doubt whether the brokors who post at
>DigElementaryParticles.com can actually deliver.
>
>Without the use of monopoles, I suspect that you'll run into the same
>problem which prevents truely isotropic antennas from ever being
>built... there's no way to construct the resulting field without
>having a discontinuity in it somewhere.

You can build an isotropic loudspeaker, but unfortunately space
doesn't support EM pressure waves.

You can make a spherical electric field, and maybe spherical gravity
waves.

Suppose you put a small conductive sphere inside a bigger conductive
sphere. If there were an AC voltage between them, you'd have current
flowing from the inner to the outer with perfect symmetry. Would that
induce a corresponding magnetic field inside? I suppose not...
everything would cancel. And besides, there's no way to apply the
voltage to the inner sphere without breaking the symmetry.

I suppose I ought to get back to work. Trying to get a Spartan6 to
configure from serial flash, no luck so far.

John


From: The Great Attractor on 3 Mar 2010 22:52
On Wed, 03 Mar 2010 14:38:30 +0000, Dirk Bruere at NeoPax
<dirk.bruere(a)gmail.com> wrote:

>On 03/03/2010 07:34, Ken Weston wrote:
>> What type of coil geometry would be required to create (or best
>> approximate) a contained, 1 metre diameter, spherical EM field of
>> several millgauss?
>>
>> Thanks for any suggestions.
>>
>> Ken Weston
>
>Well, choose a spherical container made of iron or mu-metal.
>Because otherwise magnetic fields propagate to infinity
>If you want uniformity, that is an additional impossibility.


I am sure that magnetic and electromagnetic planetoids not orbiting any
nearby star would have a fairly spherical flux/field propagation. It
would have to be pretty far away though.
From: Robert Baer on 4 Mar 2010 03:29
Ken Weston wrote:
> What type of coil geometry would be required to create (or best
> approximate) a contained, 1 metre diameter, spherical EM field of
> several millgauss?
>
> Thanks for any suggestions.
>
> Ken Weston
Is this the start of creating a (spherical) force field, similar to
that alluded to in some SF stories?
In short, how close are we to doing anything like that NOW?
From: Robert Baer on 4 Mar 2010 03:30
John Larkin wrote:
> On Wed, 03 Mar 2010 07:34:29 GMT, kenweston(a)radcliffs.com (Ken Weston)
> wrote:
>
>> What type of coil geometry would be required to create (or best
>> approximate) a contained, 1 metre diameter, spherical EM field of
>> several millgauss?
>>
>> Thanks for any suggestions.
>>
>> Ken Weston
>
> Is there such a thing as a spherical magnetic field? Where would all
> the vectors point?
>
> John
>
The question is: is it an INNIE or an OUTIE?
From: whit3rd on 4 Mar 2010 14:04
On Mar 4, 12:29 am, Robert Baer <robertb...(a)localnet.com> wrote:

>    Is this the start of creating a (spherical) force field, similar to
> that alluded to in some SF stories?
>    In short, how close are we to doing anything like that NOW?

It's a common commercial item. Called a 'ball bearing', sphericity
is available in high accuracy, forces on the exterior can be quite
high without causing any distortion.

Of course, in SF stories, sometimes there's a force field that
has lots of other properties than 'spherical'. Like, the field is
bigger than the generator, it turns ON and OFF easily... stuff
like that.
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