“Principles of Gas Filled Tubes” Vacuum Tubes Radio Technician Training Film 44124 (1945)

Synopsis

This animated film presents the theories of ionization as they are applied to gas filled or vacuum tubes. It was produced by the Division of Visual Arts of the U.S. Office of Education (:14). It opens with a display of a vacuum diode in which electrons are emitted by a cathode (:43) and attracted by a positively charged anode (:44). The number of electrons depend on the amount emitted from the cathode, the potential difference between the anode and the cathode and the negative space charge from the electrons in the stream (:52). The negative space charge limits the flow of the electrons from the cathode to the anode (1:22). In order to reduce it’s limiting effect, a small amount of mercury vapor or an inert gas is added (1:33) making it a gas filled tube (1:41). When the cathode is heated electrons are emitted (1:48). Electrons will return the to cathode if there is no positive potential in the anode (1:56). When a small amount of positive potential is included, electrons will move to the anode (2:08). Electrons move from cathode to anode and atoms of gas move around randomly (2:28). The tube will begin to glow and the current will increase if the anode potential is increased enough (2:40). The tube is said to fire or discharge (2:50). Within the tube, electrons collide with the atoms of gas causing a temporary disturbance of the orbit of the gas atoms (3:05) though they return to normal orbit quickly. Light is released during these collisions (3:35). Some of the electrons…

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Details

Running time

14 minutes

Collection

Ephemeral Films

Subjects on the Internet Archive

• Stock Footage