Re: Radioactive SparkPlugs

[Maurice Barnhill <mvb@UDel.Edu>]

LUDWIK KOWALSKI wrote:
> I do remember reading somewhere about using alpha-radioactive sources
> at the top ends of lightning rods. Can somebody confirm this? The
> purpose
> of using them this way is less obvious than in spark plugs.

Lightning discharges to the ground go from a pool of excess charge in
the cloud to a pool of induced excess charge of the opposite sign on the
ground. The major purpose of lightning rods is to drain any excess
charge off a building into the air before enough builds up to cause a
discharge.  [If this role fails, the rod had better have a connection to
the ground that is large enough to take the entire discharge around the
outside of the building. However, taking the lightning around the
building is a backup mode, not a primary mode.]  The rods are sharp so
as to cause at their tips a large electric field capable of ionizing the
air.  The ions in the air then carry the charge away at a
noncatastrophic rate.  A radioactive source on the tip of the rod would
help generate ions in the air around the lightning rod and perhaps
enhance the dispersion of charge off the building and into the air,
helping to prevent a lightning strike from occurring at all. 

-- 
Maurice Barnhill, mvb@udel.edu                
http://www.physics.udel.edu/~barnhill/          
Physics Dept., University of Delaware, Newark, DE 19716