needle valve in the carburetor float circuit is an
OIL GAGE--An indicating device that indicates the
example.
pressure of the oil in the lubrication system. Also, a
bayonet-type rod to measure oil level in the
NEGATIVE TERMINAL--The terminal from which
electrons depart when a circuit is completed from
this terminal to the positive terminal of a generator
OIL GALLERY--A pipe or drilled passageway that
or battery.
transports oil from one area to another in an engine.
NEGATIVE--A term designating the point of lower
OIL PAN--The lower part of the crankcase in which a
electrical potential when the potential difference
reservoir of oil is maintained.
between two points is considered.
OIL PUMP--The pump that transfers oil from the oil
NEOPRENE--A synthetic rubber highly resistant to
pan to the various moving parts in an engine.
oil, light, heat, and oxidation.
OIL SLINGER--A device mounted to a revolving
NEUTRALIZATION NUMBER--A measure of the
shaft such that any oil passing that point will be
total acidity or basicity of an oil; this includes
thrown outward where it will return to the point of
organic or inorganic acids or bases or a
origin.
combination of them.
OIL STRAINER--A strainer placed at the inlet end of
NEUTRON--A neutral-charge particle forming part
the oil pump to strain out dirt and other particles,
of an atom.
preventing these from getting into moving engine
parts.
NO-SPIN DIFFERENTIAL--A special type of dif-
ferential that prevents the spinning of one of the
OTTO CYCLE--The four-stroke cycle composed of
driving wheels even if it is resting on smooth ice.
intake, compression, power, and exhaust strokes.
NONFERROUS METALS--All metals containing
OVERFLOW TANK--A special tank in the cooling
very little or no iron.
system (a surge tank) to permit expansion and
contraction of engine coolant without loss.
NORTH POLE--The pole of a magnet from which
the lines of force are assumed to emanate.
OVERHEAD VALVE--A valve mounted in the head
above the combustion chamber.
NOZZLE--An orifice or opening in a carburetor
through which fuel feeds into the passing airstream
OVERLOAD BREAKER--In an electrical circuit, a
on its way to the intake manifold.
device that breaks or opens a circuit if it is
overloaded by a short, ground, or use of too much
OCTANE RATING--A measure of the antiknock
equipment, etc.
value of engine fuel.
OVERRUNNING CLUTCH--(1) A type of drive
ODOMETER--The part of the speedometer that
mechanism used in a starter that transmits cranking
measures, accumulatively, the number of vehicle
effort but overruns freely when the engine tries to
miles traveled.
drive starter. (2) A special clutch used in several
OHMMETER--A device for measuring the resis-
mechanism that permits a rotating member to turn
tance of a circuit or electrical machine.
freely under some conditions but not under other
conditions.
OHM--A measure of electrical resistance. A con-
ductor of 1-ohm resistance will allow a flow of 1
OXIDATION--The process by which oxygen unites
ampere of current when 1 volt is imposed on it.
with some other substance, causing rust or cor-
rosion.
OIL CONTROL RINGS--The lower rings on the
piston that are designed to prevent excessive
PACKING--A class of seal that is used to provide a
amounts of oil from working up into the com-
seal between two parts of a unit which move in
bustion chamber.
relation to each other.
OIL COOLER--A special cooling radiator through
PARALLEL CIRCUIT--Two or more electrical
which hot oil passes. Air also passes through
devices connected to the same pair of terminals so
separate passages in the radiator, providing cooling
that separate currents flow through each; electrons
of the oil.
AI-16
