Van de Graaff and Lightning Rods
Name: John A.
Date: Sunday, September 15, 2002
Years ago I saw an experiment using a Van De Graaff
generator wherein a pointed rod repelled static electricity and when a
rounded tip was installed over the point, the static jumped to the
rod. The purpose of the experiment was to show the importance of having
the rod pointed on the end, and seemed to imply that it kept lightning
from striking, rather than carry the charge to ground, which seems to be
the conventional wisdom.
Have you ever observed this experiment? What were the results?
Yes, I know the experiment. It illustrates that the electric field is
larger wherever a conductor has a smaller radius and is greatest at
sharp points. The high electric field can cause electrons to be
pushed off (or strongly attracted to) the pointed rod. Pointed rods
do indeed tend to keep lightning from striking, but it is precisely
because the large electric fields generate large currents, which then
reduce the charge in the clouds and so prevent lightning. If you
could remove all the excess charges from the clouds, there would be no
lighting at all.
Best, Dick Plano
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Update: June 2012