The Geissler tube is a glass tube for demonstrating the principles of electrical discharge.

Description

The tube was invented by the German glassblower Heinrich Geissler in 1857.

The Geissler tube was an evacuated glass cylinder with an electrode at each end. Geissler tubes contain a combination of one of the following: rarefied (thinned) gasses such as neon, argon, or air, or conductive liquids or minerals. When a high voltage is applied to the terminals an electrical current flows through the tube. The current will disassociate electrons from the gas molecules, creating ions and when electrons recombine with the ions different lighting effects are created. The light will be characteristic of the material contained within the tube and will be composed of one or more narrow spectral lines.

Application

They were mass produced from the 1880's as entertainment devices, with various spherical chambers and decorative serpentine paths formed into the glass tube. When the tube was handled (the terminals were insulated) the shape of the plasma changed. Some tubes were very elaborate and complex in shape and would contain chambers within an outer casing

If these were spun at high speed a visual disk of color was seen due to persistence of vision. (Somewhat similar devices in the form of stationary globes are now produced and sold for personal amusement.)

As an educational tool they are also used to demonstrate the movement of electrons and the principles of a vacuum. Geissler tubes have had a large impact on the development of such instruments as the x-ray tube, the Electrotachyscope, neon signs, mass spectrometry and some forms of the light bulb, all of which use related vacuum and discharge principles.

Influence

William Crookes developed a modification of the Geissler tube into what is known as the Crookes tube to demonstrate and study cathode rays. This device was further developed into the cathode ray tube with applications in electronics development and diagnosis, and in radar and television displays.

The Geisler Tube is the basis of the neon tube display sign and other lamps such as low and high pressure sodium vapor, mercury vapor, xenon flash, and modern automotive gas-discharge headlamps. Ultraviolet light produced by certain gases is used to excite phosphors in the fluorescent lamp and in variously colored advertising tubes (generically called "neon" signs).

See also

• Neon sign
• Cathode ray tube (CRT)
• Crookes tube
• William Crookes
• X-ray tube

External links

• Sparkmuseum: Crookes and Geissler Tubes
• Instruments for Natural Philosophy: Geissler Tubes
• Mike's Electric Stuff: Geissler Tubes
• The Cathode Ray Tube site