| Electrical discharges through
air are the first
kind of clean artificial light.
The rarefied gas electric discharge tube was
discovered by Nollet in 1740.
Further work was done on this lighting
technique by Faraday, Geissler and Edison
before the end of the 19Th. century.
With the help of Sprengel's Mercury siphon
vacuum pump of 1865 the development of the
illuminated city of night began.
Close-up of a neon
| An electric spark
is held small by the pressure of the
surrounding air. The discharge shown here has about
2500 volts across the electrodes with a current of about
4 miliamps. The current limit is set by series resisters.
As the air expands, the
As the air is given more room by the pump,
Note, plans for a simple power supply are underway.
There are plenty of
books and perhaps some people around schools who have knowledge that can
lead the building of high voltage power supplies of the kind needed for this
The voltages used here are
potentially dangerous. Connect clip leads between
the lamp and the supply terminals before plugging in the power supply.
| Cartridge fuses of this type are a good source
of short lengths of small diameter glass tubes.
Get a number of fuses to practice on.
| Clean the remaining glue from the glass
tube ends with acetone-moistened paper
Make sure to clean all lint and moisture
from all mating surfaces.
Assemble in a dust and lint free area.
Silicone grease could assist assembly
and sealing. A solid 1/4" Dia rod can be
used instead of the soldered tube segment
as shown to the right side of this picture.
| The tube is ready for connection to the
pump and power supply.
| Old tube type lasers are now obsolete
and many of the tubes have
gone bad. Now many of the power supplies are unpaired with no
further purpose. Surplus dealers and some flea market venders sell
them for a buck.
These electrical connections
should be made before applying power.
Do not leave out the 25 K ohm series ballast resister.
| Rarefied nitrogen gas
a violet light when a current
passes through it. This turns to a
pale blue gray when water vapor
given off by the internal surfaces
of the setup, replacing the dry
These pictures were taken when
There is a considerable, but
An experiment was tried using a
As the air becomes more
|| This electrical discharge is
affected by magnets.
Here is a current flowing in a
gas which is free to move about.
Just as an unconstrained wire
near a strong magnet moves
when a current passes trough,
this discharge will show the
magnetic deflection principle.
The larger tube shown here has
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