Glow Discharge Tube

The “Glow Discharge” Tube demonstrates electrical effects in a low pressure gas. Nothing happens in the tube at normal (or near normal) atmospheric pressure. However, as you reduce the pressure in the tube, it begins to glow pinkish-orange. Decrease the pressure further, and the glow breaks up into light and dark spaces. After this, the orange glow disappears completely leaving behind a blue violet glow that slowly gets dimmer until the tube is once again dark, except this time at a low pressure.

The magnet allows you to demonstrate that moving charges can be deflected by a magnetic field. (Look at the meters for an indication of the electrical current and gas pressure in the tube.)

Airplane windows have trapped gases between the panes. Have you ever noticed the “rainbow” effect when looking out from a plane’s window at high altitudes? How would you explain this?

How does the reduced atmospheric pressure affect the gases trapped in the double-paned windows of aircraft?

Questions to Ask

What subatomic particle of the atoms of the gas create the glowing effect?

What effect does the magnet have on the atoms?

What does the change in pressure do to the energy of the particles?

Relevant Arkansas Science Frameworks

PS 7.3.4, PS 7.3.5, PS.5.5.1, PS.5.8.2, PS7.8.9, PS.7.8.10, PS 7.8.11, (PS 7.K.4, PS 7.1.6, PS 7.1.7, ) C.1.PS.3, C.1.PS.7

"Mini-Vibe" — An activity to do at home or in the classroom