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The ratio between the speeds of the crankshaft and the propeller shaft is found by dividing the sum
of the teeth on the ring gear and the sun gear by the number of teeth on the sun gear. Neither the number of
teeth on the planetary gears nor the number of planetary gears rotating around the sun gear enters into the
computation for the gear ratio.
plan position indicator. See PPI.
plan view. The top view of an object in an orthographic projection.
plaque (battery component). Powdered nickel used as a base for the active elements in both the positive
and negative plates of an aircraft nickel-cadmium battery. Plaque is forced by heat and pressure to bond to
a nickel wire mesh screen to form the plates for the battery.
plasma. A completely ionized gas, consisting of equal numbers of positive ions and free electrons. Plasma
is electrically neutral.
plasma arc welding. A method of welding in which the metal is heated by an electric arc whose
temperature has been greatly intensified by the injection of a gas. The plasma arc becomes a jet of high
current density that produces temperatures of up to 60,000°F (33,316°C). One of the chief advantages of
plasma arc welding is the concentration of this extreme heat which allows parts to be welded with a
minimum of distortion.
plasma engine. An engine having applications for space travel. Neutral plasma, accelerated and directed by
external magnetic fields, interacts with the magnetic fields produced by current flowing through the
plasma.
plasma generator. A device, such as an electric arc chamber, that generates an extremely large amount of
heat and changes neutral gases into plasma.
plasma torch. A torch in which plasma gas is injected into an electric arc formed between two electrodes
in a chamber. The stream of hot gases leaves the torch at an extremely high speed through an orifice in the
negative electrode. This high-velocity, high-temperature stream can be used for welding, cutting, or
spraying molten metal. The temperature produced by a plasma torch can be as high as 60,000°F.
plasticizer (finishing material constituent). Materials used in a lacquer finishing system to give the film
flexibility and resilience.
plastic (material condition). The condition in which a material is capable of being shaped or formed. A
material in its plastic condition is normally in a semi-solid state.
plastics. The generic name for any of the organic materials produced by polymerization. Plastics can be
shaped by molding or drawing.
Plastic Wood. The registered trade name for a form of wood filler made of wood fibers mixed with a
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 444
synthetic resin. Plastic wood is used to fill cracks and holes in wood. When it hardens, it can be worked
with ordinary woodworking tools and can be finished to match the wood it is used to fill.
plate (electron tube component). The anode of an electron tube. A high positive voltage on the plate
attracts electrons from the cathode. This flow of electrons is controlled by the voltage on grids located
between the cathode and the plate.
plate current (electron tube current). Current that flows between the cathode and plate in an electron
tube.
plate glass. A thick, flat, high-quality sheet of glass. Plate glass is used for windows where strength and
undistorted vision are necessary.
plate power supply (electron tube equipment). A high-voltage, positive DC power supply for electronic
equipment using electron tubes (vacuum tubes). Plate power supplies are usually called B+ power supplies.
plate resistance (electron tube specification). A dynamic value found by dividing the change in plate
voltage by the change in plate current caused by the voltage change. No conditions other than the voltage
and current are allowed to change when making this measurement.
plate saturation (electron tube condition). The condition in an electron tube in which the plate, or anode,
is attracting all of the electrons being emitted by the cathode.
plating (metal surface treatment). The process in which a thin coating of one metal is electrolytically
deposited on the surface of another. Cadmium and chromium are used to plate steel parts to protect the steel
from corrosion. Chromium also makes the surface of the steel resistant to wear.
platinum. A heavy, silvery-white, metallic chemical element that is resistant to nearly all acids. Platinum’s
symbol is Pt, its atomic number is 78, and its atomic weight is 195.09. Because platinum is able to
withstand extremely high temperatures, it is used as the electrodes in some fine-wire spark plugs.
Platinum’s appearance is pleasing, and it is so durable it is used for jewelry.
　
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