From: Richard Koolish (koolish@bbn.com)
Date: 12/12/01-09:27:33 AM Z
I'm going to point you to some rather mathematical web pages that explain
the electric field from point, line and plane sources. The bottom line is
that a point source is 1 over R squared, a line source is 1 over R and
a plane source is constant. The text below the URLs are quotes from the
web pages, not my comments.
Note that in the real world, a fluorescent tube is not an infinite line and
a light bank is not an infinite plane, but can act like them if you are close
enough. If you move far away, the behavior changes.
Point source:
http://musr.physics.ubc.ca/~jess/hr/skept/Gauss/node1.html
"The flux from an isotropic source points away from the centre and falls
off proportional to the inverse square of the distance from the source."
Line source:
http://musr.physics.ubc.ca/~jess/hr/skept/Gauss/node5.html
"The electric field from a cylindrically symmetric charge distribution
points away from the central line and falls off proportional to the inverse
of the distance from the centre."
Plane source:
http://musr.physics.ubc.ca/~jess/hr/skept/Gauss/node6.html
"Note the interesting trend: a zero-dimensional distribution (a point)
produces a field that drops off as r-2, while a one-dimensional
distribution (a line) produces a field that drops off as r-1. We have to
be tempted to see if a two-dimensional distribution (a plane) will give us
a field that drops off as r0 -- i.e. which does not drop off at all with
the distance from the plane, but remains constant throughout space. This
application of GAUSS' LAW is a straightforward analogy to the other two,
and can be worked out easily by the reader. ;-)"
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