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Re: Radioactive SparkPlugs



-----Original Message-----
From: LUDWIK KOWALSKI <KOWALSKIL@alpha.montclair.edu>
To: phys-l@atlantis.uwf.edu <phys-l@atlantis.uwf.edu>
Date: Thursday, January 29, 1998 11:43 PM
Subject: Re: Radioactive SparkPlugs


Following Williame's message I may add that gaps used to be very common
when radios were connected to long antenna wires. I remember observing
sparks on stormy days; a discharge accress a spark was a protection
for the radio, I suppose.

These were (still are) called lightning arrestors and provide a path to
ground through a spark gap. Nowadays, varistors and even neon bulbs are
used in the same way to protect equipment from voltage surges. Eg: NE51
neon bulbs are commonly used to protect ECG front end circuitry from
defibrillator voltages; they are almost perfect insulators until a firing
voltage of about 70 volts ionizes the neon and turns them into very good
conductors. When the high voltage pulse is gone, they revert to their
insulating condition.

Bob Sciamanda sciamanda@edinboro.edu
Dept of Physics trebor@velocity.net
Edinboro Univ of PA http://www.edinboro.edu/~sciamanda/home.html
Edinboro, PA (814)838-7185