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Re: I need help.



I'm not sure what your response means. The theory for a charged rod
would predict a 1/r dependence of the field, whereas for a charge sphere
you would expect 1/r squared. The experiment gave a result of 1/r,
hence my conclusion that the sheet is a 2D space, and represents the
field in a plane perpendicular to the rod.

Could you explain your concern more fully?

joe

On Wed, 20 Feb 2002, kowalskil
wrote:

Joseph Bellina wrote:

Since the flow lines all lie in the plane of the paper, it seems to me
that the situation is a 2 dimensional one.
Let me describe an experiment I did some time ago which supports this
claim.
Construct a ring of conducting paint, and put a dot of conducting paint
in the center. Measure the potential as a function of distance from the
center, plot the curve, differentiate it by drawing some tangent lines,
and then plot the slopes as a function of distance on log-log paper. Of
course now you would do it with a computer. The slope of the resulting
line is -1, so the electric field falls off as 1/r, which is the
characteristic of an infinite rod. In this sense the paper can be
seen as a perpendicular cut in the space around a charged rod.

And, consequently, you would expect the theoretical curve (b) to
match the experimental line. But this did not happen. Why?
Ludwik Kowalski


Joseph J. Bellina, Jr. 219-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556