the Aviation Dictionary

positive terminal - The terminal of a battery or power
source where electrons enter the source after they have
passed through the external source.
positive transfer of learning - Since students interpret
new things in terms of what they already know, some
degree of transfer is involved in all learning. During a
learning experience, knowledge or skills they have
gained in the past can aid students.
positive vorticity - In weather, the vertical component
of vorticity (i.e., a measure of how rapidly the air is
spinning) leading to cyclonic flow. It is associated
with upward air motions.
positive-displacement pump - A fluid pump that
moves a soecific amount of fluid each time it rotates.
Examples of positive-displacement pumps include gear
pumps, gerotor pumps, and vane pumps.
positron - The positive counterpart of an electron,
which has the same mass and spin characteristics as an
electron, but with a positive electrical charge.
post exit thrust reverser - A thrust reverser used to
reverse the hot exhaust stream of a gas turbine engine
to help slow the airplane during landings.
postcure - During the curing cycle of a manufactured
composite component, the postcure is an additional
elevated temperature soak to improve the mechanical
properties.
positive terminal . power amplifier
has a high moisture content. Potential instability is one
of the two basic requirements for the formation of a
thunderstorm; the other is initial lift.
potentiometer - 1. A variable resistor having both ends
and its wiper in the circuit. Used as a voltage divider.
2. An instrument used for measuring differences in
electrical potential by balancing the unknown voltage
against a known variable voltage.
potentiometer ohmmeter - An ohmmeter circuit in
which resistance is measured by placing a known
voltage across a standard resistor; then the circuit is
opened and the unknown resistor is placed in series.
The voltage drop across the standard resistor is read
and displaced on the meter as ohms.
pot-life - In composites, the length of time that the resin,
mixed with catalyst, will be in a workable state.
potted circuit connector - An electrical circuit
connector protected by encapsulating it with an
insulating potting compound.
potting compound - 1. A resin having filler capability,
used to fill cells when making minor repairs to
damaged honeycomb panels. 2. A non-hardening,
rubber-like material used to moisture proof and protect
the wires in certain electrical plugs.
pound - A measure of mass equal to approximately
0.454 kg.
pot life - The usable life of a resin. The time before it pour point - 1. The lowest temperature at which a fluid
begins to thicken after the catalyst and accelerator have will pour without disturbance. 2. The lowest
been added.
temperature at which oil will gravity flow.
potassium -A metallic element with a symbol of K and powder metallurgy - A development that makes use of
an atomic number of 19.
powdered metals rather than ingots. A process used to
produce superalloys for high heat, high strength turbine
potential - The electrical pressure or voltage caused by
components and for bearing material (sintered
dissimilar metals in an acid solution or an electrolyte.
bearings). -
potential barrier - The difference in forward bias
powdered-iron core - A molded, magnetic powdered
potential between the N side and the P side of a
iron mixed with a binder. Used in magnetic
semiconductor. This is the amount of forward voltage
applications when high permeability and low eddy
necessary to begin current flow through a device. The
current losses are desired.
nominal amount of the potential barrier is 0.3 volts for
a germanium device and 0.7 volts for a silicon device. power (P)- 1. The time-rate of doing work. Force times
OK, but fails to mention the effect of temperature.
distance, divided by time. Power can be expressed in
terms of fo~t-~ouids of work per minute, or in
potential difference - The difference in voltage that
horsepower (HP). One HP is 33,000 ft.-lbs. of work per
exists between two terminals or two points of differing
minute. 2. The basic unit of electrical power is the watt,
potential.
and 746 watts of electrical power is equal to one
potential drop - A drop in voltage in an electrical mechanical horsepower. In electrical problems, power
circuit caused by the resistance of current flow through is the product of voltage (E) times current (I) (P = E X
a resistance.
I). Power in watts delivered to a circuit varies directly
with the square of the applied voltage and inversely
potential energy - The energy possessed by an object
with the circuit resistance.
because of its ~osition, configuration. . or chemical
arrangement - of iis constituents.
power amplifier - An electronic device designed to
create an increase in power (voltage times amperage)
potential instability - A layer of air that is not only
as opposed to an amplifier designed to create an
potentially unstable, it is conditionally unstable, and
increase in voltage.
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