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definition of: GLOW LAMP

What is GLOW LAMP?

Glow Lamp is a glass envelope filled with gas which contains two or more electrodes.

Glow lamps are cold-cathode devices which require no heater or filament.

Glow lamps produce a very interesting, mild, beautiful colorful glow.

Color of glow depends on the gas combination used.

Pure neon produces an orange/red glow, pure argon produces a purple glow.

The electrodes are separated by gap of about 1/8th inch inside the gas envelope.

If a variable voltage is applied across the electrodes and increased to about 50 volts, basically no current will flow.

Eventually as voltage is increased, positive ions are attracted to the cathode which has a negative charge.

As voltage increases, electrons are liberated in the generation of positive ions which are attracted to the positive anode.

At a certain voltage (the Breakdown Voltage) enough ion velocity is attained were electrons dislodge increased proportions of ions and as the gas breaks down it conducts electricity (and a corona forms around the cathode) while a current "run-away" or "avalanche" occurs.

This avalanche is self destructive if uncontrolled, so an in-series current-limiting resistor must be used, which are built in to most screw based glow lamps rated for use at specific line voltage, otherwise you'll have to supply the necessary resistor.

Most glow lamps can be used from Breakdown Voltage to 600 volts when you properly select current limiting resistor.

When a Glow Lamp is operated in a completely dark environment, a phenomenon called dark-effect occurs which greatly changes (raises) the break-down voltage.

Gas lamps perform poorly on altitudes over 70,000 feet as low atmospheric pressure encourages outside corona and arcing.

references for this page: GLOW LAMP, ARGON LAMP, GAS DIODE, GAS TUBE, GLOW TUBE, NEON, NEON LAMP

references to this page: BREAKDOWN VOLTAGE, CORONA, DARK-EFFECT, ENCODINGS PHILIPS OLD BULBS, MAINTAINING VOLTAGE