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Some globes have a control knob that varies the amount of power going to the center electrode. At the very lowest setting that will light or "strike" the globe, a single tendril is made. This single tendril's plasma channel engages enough space to transmit this lowest striking energy to the outside world through the glass of the globe. As the power is increased, this single channel's capacity is overwhelmed and a second channel forms, then a third, and so on. Placing a finger tip on the glass creates an attractive spot for the energy to flow, because conductive human body (having non-ohmic resistance of about 1000 ohms at room temperature) is more easily polarized than the dielectric material around the electrode (i.e. the gas within the globe) providing an alternative discharge path having less resistance. The globe is prepared by pumping out as much air as is practical. The globe is then back-filled with neon to a pressure similar to one atmosphere. If the radio- frequency power is turned on, if the globe is "struck" or "lit", now, the whole globe will glow a diffuse red. If a little argon is added, the filaments will form. If a very little xenon is added, the "flowers" will bloom at the ends of the filaments. Applications Plasma lamps are mainly used as curiosities or toys for their unique lighting effects and the "tricks" that can be performed on them by users moving their hands around them. They might also form part of a school's laboratory equipment for demonstration purposes. They are not usually employed for general lighting. However, as of recent years, some novelty stores have begun selling a nightlight plasma lamp that can fit into a standard light socket. Bringing conductive materials or electronic devices close to a plasma globe may cause the glass to become hot. The high voltage radio frequency energy coupled to them from within the globe may cause a mild electric shock, even through a protective plastic casing. If a tinfoil hat or a coin is placed on the globe, capacitive coupling can transfer enough current through the foil or coin to give a small arc burn or light a small lamp connected to earth ground. This is possible because the globe's glass acts as a capacitor dielectric: the inside of the lamp acts as one plate, and any conductive object on the outside acts as the other capacitor plate. This is dangerous to do, can damage the globe, and presents a fire hazard. Hazards Hazards Plasma Globe A plasma globe or plasma lamp (also called plasma ball, dome, sphere, tube or orb, depending on shape) is (usually) a clear glass orb filled with a mixture of various noble gases with a high-voltage electrode in the center of the sphere. Plasma filaments extend from the inner electrode to the outer glass insulator, giving the appearance of multiple constant beams of colored light. Description
