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Re: capillary effect



At 04:38 PM 5/31/2003 -0400, you wrote:
/snip/
Let me mention an interesting capillary effect worth sharing. I took
a very thin wire and inserted it into a capillary tube. The wire ended
at the same level as the mouth of the tube. I inserted the tube into a
conducting liquid -- a solution uranium nitrate. Then I removed the
loaded tube from the liquid and placed it (with the wire and some
liquid inside) above a metallic foil. The distance between the mouth
of the tube and the foil was about 2 cm in air.

The difference of potential of several thousand volts was applied
between the wire and the foil. This produced a shower of tiny
droplets; the tube emptied after about one minute. A thin layer of
uranium nitrate was deposited on the foil. That is how thin uranium
targets were prepared for my doctoral work. The central areas
covered with uranium were usually sufficiently uniform in
thickness. This method of thin targets preparation was invented
by two researchers from Harwell Laboratory in England.
Ludwik Kowalski


This is the process now used commercially to paint for instance,
car bodies. The method is labeled "electrophoretic".
The advantages include lower paint splatter/loss than regular
spray gun painting. Moreover (if I recall), edges and points are
preferentially coated, which you will notice is in conflict with
the idea of an electric force weakening in tractive power at
an edge; the idea I mentioned for the water dielectric
capacitor.

Brian Whatcott Altus OK