Date: Fri Sep 28 19:03:48 2007

Author: Urs Lauterburg

Subject: Re: Visualization fluid for electric field lines demo

Post:
John McIntyre wrote on Fri, 28 Sep 2007

>OK, this is a stupid question, but how do you get your faculty to
>accept anything that takes five minutes of their lecture time? I
>faced emmense resistence to five seconds. (-8

John,

This is not a stupid question at all because the trend towards
everything having to happen instantaneous is indeed a questionable
one. Everything that takes some time and asks for patience and
sustained attention is rated ''unexciting''. However, I think that 5
minutes settling time for the particles in the oil to show a
geometrical electric field pattern is too long.

Actually I am pretty content with my Nakamura E-field demonstrator
and I have always wanted to add some of my own additional geometries
like a sharp spike or a mirror charge. With all these induced
dielectric dipoles though, I do find it a bit problematic that they
don't really seem to align along the electric field lines but rather
form some tree like branching structures, of course within the
overall theoretical field geometry though.

I always wondered how the ones shown in the very nice illustrations
of Tipler's book ''Physics for Scientists and Engineers'' where made.
They are really beautiful, but I suspect that the photographs taken
of the experiment have actually been photoshoped up afterwards.
Cheating is possible with photographic, movie and modeling
reproductions BUT not so much with real performed experiments !

Regards

Urs

Urs Lauterburg
Physics demonstrator
Physikalisches Institut
University of Bern
Switzerland


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