However, when maneuverability is more important than stability, as it is on some military fighters and acrobatic airplanes, the wings are set with negative dihedral (cathedral). The wings angle downward from the center.
Cathedral decreases the stability of an airplane and makes it more maneuverable.
cathode of an electrochemical cell. The active element in an electrochemical cell that is reduced, or loses oxygen in the chemical action which causes electrons to flow.
cathode of a semiconductor diode. The end of a semiconductor diode made of N-type material. When the diode is forward biased with the negative terminal of the power source connected to the cathode of the diode, electrons flow through the diode. The cathode of a semiconductor diode is identified by the bar in the diode symbol.
cathode rays. Streams of electrons emitted by the cathode in a special form of electron tube called a cathode-ray tube (CRT). These electrons are accelerated by the attraction of a positive voltage on special grids called accelerator grids. The cathode rays strike a phosphorescent material that covers the inside of the face of the tube, and when they strike it, the material glows.
Cathode-ray tubes are used as the display in computers and oscilloscopes.
cathode-ray tube. See CRT.
cathodic area. An area within a piece of metal to which electrons from the anodic area have migrated.
cathodic protection. Another name for sacrificial corrosion. A material that is more anodic than the material being protected is attached to or plated on the material. This becomes the anode and is corroded, while the part being protected is the cathode and it is not damaged.
cation. A positive ion that moves toward the cathode in the process of electrolysis.
catwalk. A narrow walkway inside a structure that allows a person to move through an area that is otherwise inaccessible.
caustic material. Any material that can eat away another material by chemical action. Both strong acids and strong aklalis are caustic materials.
caustic soda. A common name for sodium hydroxide, NaOH. Caustic soda is often called lye.
cavitation. A condition that exists in a fluid pump when there is not enough pressure in the reservoir to force fluid to the inlet of the pump. The pump picks up air instead of fluid.
cavity. An empty (unfilled) space. A cavity is the same as a hole.
C-battery (radio battery). A small, low-voltage battery used in some of the older, battery-powered, tube-type radios to provide a grid bias voltage for some of the vacuum tubes.
C-batteries have generally been replaced by a method of biasing the tubes with the voltage drop across a resistor.
C-check. See maintenance checks.
CCL (convective condensation level). The lowest level at which condensation will occur as a result of convection due to surface heating.
When condensation occurs at this level, the layer between the surface and the CCL will be thoroughly mixed, the temperature lapse rate will be dry adiabatic (3°C per 1,000 feet), and the mixing ratio will be constant.
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