Neon Lamp

Neon Lamp, glass bulb or tube containing the gaseous element neon at low pressure, and two metallic electrodes. The lamp produces a reddish-orange glow when an electric current, applied across the electrodes, is raised in voltage to the point at which it ionizes the gas in the tube (see Electric Lighting; Ionization). The voltage at which the lamp glows varies with the design of the tube. When gas in the tube is ionized, the voltage drop across the tube is nearly constant, regardless of the amount of current flowing through the tube. For this reason very small neon lamps are often used in electronic devices as voltage regulators to provide a constant direct-current voltage. These lamps are also used sometimes as pilot lamps to indicate whether or not a piece of electric equipment is drawing current.

Another kind of neon lamp is a glass tube containing ionized neon at very low pressure. The tube shines with a brilliant red glow if a high-voltage alternating current is applied to electrodes sealed in the ends of the tube. Neon lamps of this type, and lamps using other gaseous elements such as, argon or krypton, are used extensively for advertising signs. See Luminescence.