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GLOW DISCHARGE
TUBE demonstrates electrical effects in a low-pressure gas. The
visitor can vary the voltage and air pressure in a large cylindrical
tube. If gas is leaked into the tube up to atmospheric (or almost
atmospheric) pressure, all glowing ceases. As the vacuum pump reduces
the pressure in the tube, it begins to glow pinkish-orange. As the
pressure further decreases, the glow breaks up into light and dark
spaces (Crooke's dark spaces). After this phenomenon, the orange
glow disappears completely, leaving behind a blue violet glow which
slowly gets dimmer until the tube is once again dark, except this
time at a low pressure. A magnet hangs from the exhibit which allows
the visitor to demonstrate that moving charges can be deflected
by a magnetic field. Meters are provided which give an indication
of the current flowing in the tube as well as the gas pressure.
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