Search results
Results From The WOW.Com Content Network
Artificial willemite was used as the basis of first-generation fluorescent tube phosphors. When doped with manganese ions, it fluoresces with a broad white emission band. Some versions had some of the zinc replaced with beryllium. In the 1940s it was largely replaced by second-generation halophosphors based on fluorapatite. These, in turn have ...
Fluorescent lamp, a device with negative differential resistance. [1] In operation, an increase in current through the fluorescent tube causes a drop in voltage across it. If the tube were connected directly to the power line, the falling tube voltage would cause more and more current to flow, causing it to arc flash and destroy itself.
Fluorescent penetrant inspection (FPI) is a type of dye penetrant inspection in which a fluorescent dye is applied to the surface of a non-porous material in order to detect defects that may compromise the integrity or quality of the part in question. FPI is noted for its low cost and simple process, and is used widely in a variety of industries.
[1] [3] To prevent this, fluorescent tubes are connected to the power line through a ballast. The ballast adds positive impedance (AC resistance) to the circuit to counteract the negative resistance of the tube, limiting the current. [1] Several American magnetic ballasts for fluorescent lamps. The top is a rapid start series autoregulator ...
The very small capacitance between overhead lines and a fluorescent lamp tube (in the foreground of the photo) provides enough current to cause the lamp to glow. Ungrounded metal objects close to electric field sources such as neon signs or conductors carrying alternating currents may have measurable voltage levels caused by capacitive coupling.
T12 fluorescent tubes. The first two are rapid start, (for "tombstone" and socket holders respectively) while the third is an instant-start lamp. The instant-start has a characteristic, rounded, single pin, for plugging into the spring-loaded socket holders. Instant start fluorescent tubes were invented in 1944. Instant start simply uses a high ...
The two major innovations of the unit were the high-frequency ballast, which gave the lights greater intensity and eliminated flicker commonly found in off-the-shelf fluorescent tubes, and the Kino Flo tubes, which contained a number of special phosphors designed to eliminate the characteristic tints in the magenta-green spectrum which are present in most domestic fluorescent lights. [3]
Today, electric arcs are used in many applications. For example, fluorescent tubes, mercury, sodium, and metal halide lamps are used for lighting; xenon arc lamps are used for movie projectors and theatrical spotlights. Formation of an intense electric arc, similar to a small-scale arc flash, is the foundation of exploding-bridgewire detonators.