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neon bulb. A type of glow lamp made of two insulated electrodes inside a glass envelope filled with neon
gas. Neon gas does not conduct electricity until the voltage across the electrodes rises to the ionization, or
firing, voltage of the neon. When this voltage is reached, the neon gas ionizes and conducts.
Electrons flowing through the ionized gas cause it to glow with a reddish-orange light. The gas
continues to glow until the voltage across the electrodes drops to a value lower than its ionization voltage.
neon-bulb oscillator (electronic circuit). A relaxation oscillator using a neon bulb to produce oscillation.
The bulb is installed in parallel with a capacitor. When DC voltage is applied to the circuit through a
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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resistor, the voltage across the bulb and capacitor rises until the ionization voltage of the bulb is reached.
As soon as the neon gas ionizes, it short-circuits the capacitor, and the voltage drops to the deionization
voltage, at which time conduction stops. The waveform of a neon-bulb oscillator is a sawtooth.
neoprene. A type of synthetic rubber made from petroleum. Neoprene is superior to natural rubber and
other synthetic rubbers because of its resistance to damage from petroleum products.
neptunium. A silvery, metallic, naturally radioactive chemical element. Neptunium’s symbol is Np, its
atomic number is 93, and its atomic weight is 237.0482. Neptunium is found as a trace element in uranium
ores and is produced synthetically in nuclear reactions.
net thrust (turbine engine specification). The thrust produced by a turbojet or turbofan engine in which
the acceleration factor is the difference between the velocity of the incoming air and the velocity of the
exhaust gases leaving the engine. Net thrust is actually the change in momentum of the mass of air and fuel
passing through the engine.
neutral axis (structures). The neutral axis of a piece of material being bent is a plane within the material
along which there is no stress. The neutral axis is located approximately halfway (actually 44.5% of the
thickness of the material) from the inside of the bend. The material on the outside of the bend is under a
tensile stress, and that on the inside is under a compressive stress. There is no stress along the neutral axis.
neutral conductor (electrical power system). A conductor in both three-wire single-phase, and
Y-connected three-phase electrical systems in which the voltage is the same between it and any of the other
conductors. The neutral conductor in a three-wire single-phase system is normally grounded with 110 volts
between either line and the neutral conductor, and 220 volts between the two lines. In a Y-connected,
three-phase system, there is normally 120 volts between any of lines and the neutral conductor and 208
volts between any two of the lines.
neutral flame (oxygas welding). A flame that uses the chemically correct ratio of fuel gas and oxygen. A
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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neutral flame in an oxyacetylene torch has an almost white, rounded inner cone and an envelope of light
blue flame. Too much oxygen changes a neutral flame into an oxidizing flame, and the inner cone becomes
pointed. Too much acetylene changes a neutral flame into a carburizing, or reducing, flame, and a feather
appears around the inner cone.
neutralization (electronic circuit). The use of external circuit devices to cancel, or neutralize, the effect of
interelectrode capacitance in an electron tube.
neutral plane (electrical machine). An imaginary line perpendicular to the lines of magnetic flux passing
between the field poles of an electric motor or generator. If the brushes are mounted along this neutral
plane, the segments of the commutator they short across have the same electrical potential, and there will
be no sparking at the brushes.
neutral position of the rotating magnet (aircraft magneto). The position of the rotating magnet in an
aircraft magneto in which the poles of the magnet are directly between the pole shoes in the magneto
housing. When the magnet is in its neutral position, no magnetic flux flows through the core of the magneto
coil.
neutral static stability (aircraft stability). A condition of static stability in which an aircraft, if disturbed
from its condition of rest, will neither attempt to deviate farther from this condition nor to return to its
original condition.
neutron. A particle in the nucleus of an atom which has mass, but no electrical charge. A neutron has about
the same mass as a proton, and it adds weight to the atom, but does not affect its chemical behavior.
Neutrons serve as a “cement” to hold the protons in the nucleus of an atom.
　
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