Pressure and Gas

            The inside of a plasma globe’s glass sphere is a fairly strong vacuum. What little gas there is must have very specific properties for the globe’s effect to work, so there are only a few different types of gases that plasma globes commonly have.

            First of all, the inner Tesla coil is sometimes encased in a tiny glass ball (not to be confused with the larger outer glass ball), sometimes it isn’t; either way, the gas in the globe may make contact with it. As a result, it is important that this gas be nonreactive so it doesn’t react with the surface of the Tesla coil. This is part of why Noble Gases like Neon, Xenon, and Krypton are commonly used.

            Another important property of the gases is the color of light they emit when changing energy states. Different gases emit different colors when being “broken down” by electrons, so the color of the plasma in a plasma globe is entirely dependent on what gases are inside it.

            The pressure of the gas inside the globe is also extremely important! It can’t be too high or too low, otherwise the plasma globe won’t work as intended. The lower the pressure is, the easier it is for the electrons that shoot off the electrode to break down the gas particles into ions. Thus, if the pressure is too high, the electrons won’t be able to create any ions (and by extension, any plasma) and you won’t see anything. However, this doesn’t mean the pressure should be lowered as far as possible. The amount of gas particles in the globe affects the ability of the “streamers” you see to stay intact. A low pressure means fewer particles and a longer distance for the electrons to travel to hit them. As a result, if the pressure is too low you will simply see a glowing globe without any mini “streamers,” similar to a light bulb except nowhere near as bright.


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